XCP_ReferenceBook_V3.0_ENs
XCP – The Standard Protocol
for ECU Development
Fundamentals and Application Areas
Andreas Patzer | Rainer Zaiser
Andreas Patzer | Rainer Zaiser
XCP – The Standard Protocol for ECU Development
Date December 2016
Reproduction only with expressed permission from
Vector Informatik GmbH, Ingersheimer Str. 24, 70499 Stuttgart, Germany
© 2016 by Vector Informatik GmbH. All rights reserved. This book is only intended for personal use, but not
for technical or commercial use. It may not be used as a basis for contracts of any kind. All information in this
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XCP
The Standard Protocol
for ECU Development
Fundamentals and Application Areas
Andreas Patzer, Rainer Zaiser
Vector Informatik GmbH
Table of Contents
Introduction ........................................................................................................................................... 7
1 Fundamentals of the XCP Protocol ...........................................................................................13
1.1 XCP Protocol Layer ................................................................................................................ 19
1.1.1 Identification Field ........................................................................................................21
1.1.2 Timestamp .....................................................................................................................21
1.1.3 Data Field ...................................................................................................................... 22
1.2 Exchange of CTOs .................................................................................................................. 22
1.2.1 XCP Command Structure .......................................................................................... 22
1.2.2 CMD ................................................................................................................................ 25
1.2.3 RES .................................................................................................................................. 28
1.2.4 ERR .................................................................................................................................. 28
1.2.5 EV .................................................................................................................................... 29
1.2.6 SERV ............................................................................................................................... 29
1.2.7 Calibrating Parameters in the Slave ....................................................................... 29
1.3 Exchanging DTOs – Synchronous Data Exchange ......................................................... 32
1.3.1 Measurement Methods: Polling versus DAQ ......................................................... 33
1.3.2 DAQ Measurement Method ...................................................................................... 34
1.3.3 STIM Calibration Method ........................................................................................... 42
1.3.4 XCP Packet Addressing for DAQ and STIM ........................................................... 43
1.3.5 Bypassing = DAQ + STIM ........................................................................................... 45
1.3.6 Time Correlation and Synchronization ................................................................... 45
1.4 XCP Transport Layers ...........................................................................................................49
1.4.1 CAN ................................................................................................................................. 49
1.4.2 CAN FD .......................................................................................................................... 52
1.4.3 FlexRay ........................................................................................................................... 54
1.4.4 Ethernet ......................................................................................................................... 57
1.4.5 SxI .................................................................................................................................... 59
1.4.6 USB ................................................................................................................................ 60
1.4.7 LIN .................................................................................................................................. 60
1.5 XCP Services ............................................................................................................................ 61
1.5.1 Memory Page Swapping .............................................................................................61
1.5.2 Saving Memory Pages – Data Page Freezing ....................................................... 63
1.5.3 Flash Programming ..................................................................................................... 63
1.5.4 Automatic Detection of the Slave ........................................................................... 65
1.5.5 Block Transfer Mode for Upload, Download and Flashing .................................66
1.5.6 Cold Start Measurement ........................................................................................... 67
1.5.7 Security Mechanisms with XCP ................................................................................68
2 ECU Description File A2L .............................................................................................................71
2.1 Setting Up an A2L File for an XCP Slave ......................................................................... 74
2.2 Manually Creating an A2L File ............................................................................................ 75
2.3 A2L Contents versus ECU Implementation ..................................................................... 76
3 Calibration Concepts ................................................................................................................... 79
3.1 Parameters in Flash .............................................................................................................. 80
3.2 Parameters in RAM ................................................................................................................82
3.3 Flash Overlay ...........................................................................................................................84
3.4 Dynamic Flash Overlay Allocation .....................................................................................85
3.5 RAM Pointer Based Calibration Concept per AUTOSAR .............................................86
3.5.1 Single Pointer Concept ...............................................................................................86
3.5.2 Double Pointer Concept .............................................................................................88
3.6 Flash Pointer Based Calibration Concept .......................................................................89
4 Application Areas of XCP ............................................................................................................ 91
4.1 Model in the Loop (MIL) ....................................................................................................... 93
4.2 Software in the Loop (SIL) .................................................................................................. 94
4.3 Hardware in the Loop (HIL) .................................................................................................95
4.4 Rapid Control Prototyping (RCP) ...................................................................................... 97
4.5 Bypassing ..................................................................................................................................98
4.6 Shortening Iteration Cycles with Virtual ECUs ........................................................... 101
5 Example of an XCP Implementation ......................................................................................105
5.1 Description of Functions ....................................................................................................108
5.2 Parameterization of the Driver ........................................................................................ 110
6 Protocol Development Overview ..............................................................................................111
6.1 XCP Version 1.1 (2008) ......................................................................................................... 112
6.2 XCP Version 1.2 (2013) .......................................................................................................... 112
6.3 XCP Version 1.3 (2015).......................................................................................................... 113
The Authors..................................................................................................................................... 114
Table of Abbreviations and Acronyms .....................................................................................116
Literature ........................................................................................................................................ 117
Web Addresses............................................................................................................................... 117
Table of Figures .............................................................................................................................118
Appendix – XCP Solutions at Vector ......................................................................................120
Index ................................................................................................................................................. 122
Introduction
7
Introduction
In optimal parameterization (calibration) of electronic ECUs, you calibrate parameter values
during the system runtime and simultaneously acquire measured signals. The physical con
nection between the development tool and the ECU is via a measurement and calibration
protocol. XCP has become established as a standard here.
First, the fundamentals and mechanisms of XCP will be explained briefly and then the appli
cation areas and added value for ECU calibration will be discussed.
First, some facts about XCP:
> XCP signifies “Universal Measurement and Calibration Protocol”. The “X” stands for the
variable and interchangeable transport layer.
> It was standardized by an ASAM working committee (Association for Standardisation of
Automation and Measuring Systems). ASAM is an organization of automotive OEMs, sup
pliers and tool producers.
> XCP is the protocol that succeeds CCP (CAN Calibration Protocol).
> The conceptual idea of the CAN Calibration Protocol was to permit read and write access
to internal ECU data over CAN. XCP was developed to implement this capability via dif
ferent transmission media. Then one speaks of XCP on CAN, XCP on FlexRay or XCP on
Ethernet.
> The primary applications of XCP are measurement and calibration of internal ECU para
meters. Here, the protocol offers the ability to acquire measured values “event synchro
nous” to processes in ECUs. This ensures consistency of the data between one another.
To visualize the underlying idea, we initially view the ECU and the software running in it as a
black box. In a black box, only the inputs into the ECU (e.g. CAN messages and sensor values)
and the output from the ECU (e.g. CAN messages and actuator drives) are acquired. Details
about the internal processing of algorithms are not immediately apparent and can only be
determined from an analysis of the input and output data.
Now imagine that you had a look into the behavior of your ECU with every computation
cycle. At any time, you could acquire detailed information on how the algorithm is running.
You would no longer have a black box, but a white box instead with a full view of internal
processes. That is precisely what you get with XCP!
What contribution can XCP make for the overall development process? To check the func
tionality of the attained development status, the developer can execute the code repeatedly.
In this way, the developer finds out how the algorithm behaves and what might be opti
mized. It does not matter here whether a compiled code runs on a specific hardware or
whether it is developed in a modelbased way and the application runs in the form of a
model.
A central focus is on the evaluation of the algorithm process. For example, if the algorithm
is running as a model in a development environment, such as Simulink from The MathWorks,
it is helpful to developers if they can also acquire intermediate results to their applications,
in order to obtain findings about other changes. In the final analysis, this method enables
nothing other than read access to parameters so that they can be visualized and analyzed –
8
Introduction
and all of this at model runtime or retrospectively after a timelimited test run has been
completed. A write access is needed if parameterizations are changed, e.g. if the propor
tional component of a PID controller is modified to adapt the algorithm behavior to the
system under control. Regardless of where your application runs – focal points are always
the detailed analysis of algorithm processes and optimization by changes to the
parameterization.
This generalization can be made: The algorithms may exist in any type of executable form
(code or model description). Different systems may be used as the runtime environment
(Simulink, as DLL on the PC, on a rapid prototyping platform, in the ECU etc.). Process flows
are analyzed by read access to data and acquisition of its timebased flow. Parameter sets
are modified iteratively to optimize algorithms. To simplify the representation, the acquisi
tion of data can be externalized to an external PCbased tool, although it is understood here
that runtime environments themselves can even offer analysis capabilities.
Runtime Environment
Application
Communication
PC Tool
Figure 1:
Operating System
Fundamental
communication with
a runtime environment
The type of runtime environment and the form of communication generally differ from one
another considerably. The reason is that the runtime environments are developed by differ
ent producers and are based on different solution approaches. Different types of protocols,
configurations, measurement data formats, etc. make it a futile effort to try to exchange
parameter sets and results in all development steps. In the end, however, all of these solu
tions can be reduced to read and write access at runtime. And there is a standard for this:
XCP.
XCP is an ASAM standard whose Version 1.0 was released in 2003. The acronym ASAM
stands for “Association for Standardisation of Automation and Measuring Systems.” Sup
pliers, vehicle OEMs and tool manufacturers are all represented in the ASAM working group.
The purpose of the XCP working group is to define a generalized measurement and calibra
tion protocol that can be used independent of the specific transport medium. Experience
gained from working with CCP (CAN Calibration Protocol) flowed into the development as
well.
XCP was defined based on the ASAM interfaces model. The following figure shows a mea
surement and calibration tool’s interfaces to the XCP Slave, to the description file and the
connection to a higherlevel automation system.
Introduction
9
Upper Level
Automation System
ASAM MCD-3 MC
Measurement and
ASAM
Calibration System
MCD-2 MC
*.A2L
XCP Driver
ECU Description File
ASAM MCD-1 MC
XCP Driver
ECU
Figure 2:
The Interface Model
of ASAM
Interface 1: “ASAM MCD-1 MC” between ECU and measurement & calibration system
This interface describes the physical and the protocolspecific parts. Strictly speaking, a dis
tinction was made between interfaces ASAP1a and ASAP1b here. The ASAP1b interface,
however, never received general acceptance and for all practical purposes it has no relevance
today. The XCP protocol is so flexible that it can practically assume the role of a general
manufacturerindependent interface. For example, today all measurement and calibration
hardware manufacturers offer systems (xETK, VX1000, etc.) which can be connected via
the XCP on Ethernet standard. An ASAP1b interface – as it was still described for CCP – is
no longer necessary.
Interface 2: “ASAM MCD-2 MC” A2L ECU description file
As already mentioned, XCP works in an addressoriented way. Read or write accesses to
objects are always based on an address entry. Ultimately, however, this would mean that
the user would have to search for his ECU objects in the Master based on the address. That
would be extremely inconvenient. To let users work with symbolic object names, for example,
a file is needed that describes the relationship between the object name and the object
address. The next chapter is devoted to this A2L description file.
Interface 3: “ASAM MCD-3 MC” automation interface
This interface is used to connect another system to the measurement and calibration tool,
e.g. for test bench automation. The interface is not further explained in this document,
because it is irrelevant to understanding XCP.
10
Introduction
XCP is based on the MasterSlave principle. The ECU is the Slave and the measurement and
calibration tool is the Master. A Slave may only communicate with one Master at any given
time; on the other hand, the Master can simultaneous communicate with many Slaves.
Master
Bus
Figure 3:
An XCP Master can
simultaneously
Slave
Slave
Slave
Slave
communicate with
multiple Slaves
To be able to access data and configurations over the entire development process, XCP
must be used in every runtime environment. Fewer tools would need to be purchased, oper
ated and maintained. This would also eliminate the need for manual copying of configura
tions from one tool to another, a process that is susceptible to errors. This would simplify
iterative loops, in which results from later work steps are transferred back to prior work
steps.
But let us turn our attention away from what might be feasible to what is possible today:
everything! XCP solutions are already used in a wide variety of work environments. It is the
intention of this book to describe the main properties of the measurement and calibration
protocol and introduce its use in the various runtime environments. What you will not find in
this book: neither the entire XCP specification in detailed form, nor precise instructions for
integrating XCP drivers in a specific runtime environment. It explains the relationships, but
not the individual protocol and implementation details. Internet links in the appendix refer
to openly available XCP driver source code and sample implementations, which let you
understand and see how the implementation is made.
Screenshots of the PC tool used in this book were prepared using the CANape measurement
and calibration tool from Vector. Other process flows are also explained based on CANape, in
cluding how to create an A2L file and even more. With a costfree demo version, which is avail
able to you in the Download Center of the Vector website at www.vector.com/canape_demo,
you can see for yourself
1 Fundamentals of the XCP Protocol
13
1 Fundamentals of the XCP Protocol
14
1 Fundamentals of the XCP Protocol
Interface 1 of the ASAM interfaces model describes sending and receiving commands and
data between the Slave and the Master. To achieve independence from a specific physical
transport layer, XCP was subdivided into a protocol layer and a transport layer.
CAN
Ethernet FlexRay
SxI
USB
...
Figure 4: Subdivision of the XCP protocol into protocol layer and transport layer
Depending on the transport layer, one refers to XCP on CAN, XCP on Ethernet, etc. The
extendibility to new transport layers was proven as early as 2005 when XCP on FlexRay
made its debut. The current version of the XCP protocol is Version 1.3, which was approved
in 2015.
Adherence to the following principles was given high priority in designing the protocol:
> Minimal resource usage in the ECU
> Efficient communication
> Simple Slave implementation
> Plugandplay configuration with just a small number of parameters
> Scalability
1 Fundamentals of the XCP Protocol
15
A key functionality of XCP is that it enables read and write access to the memory of the
Slave.
Read access lets users measure the time response of an internal ECU parameter. ECUs are
systems with discrete time behavior, whose parameters only change at specific time inter
vals: only when the processor recalculates the value and updates it in RAM. One of the great
strengths of XCP lies in acquiring measured values from RAM which change synchronously
to process flows or events in the ECU. This lets users evaluate direct relationships between
timebased process flows in the ECU and the changing values. These are referred to as
eventsynchronous measurements. The related mechanisms will be explained later in detail.
Write access lets the user optimize parameters of algorithms in the Slave. The accesses are
addressoriented, i.e. the communication between Master and Slave references addresses in
memory. So, the measurement of a parameter is essentially implemented as a request of
the Master to the Slave: “Give me the value of memory location 0x1234”. Calibration of a
parameter – the write access – to the Slave means: “Set the value at address 0x9876 to 5”.
An XCP Slave does not absolutely need to be used in ECUs. It may be implemented in differ
ent environments: from a modelbased development environment to hardwareintheloop
and softwareintheloop environments to hardware interfaces that are used to access ECU
memory via debug interfaces such as JTAG, NEXUS and DAP.
Simulink
Slave
Prototype or
ECU Hardware
Slave
Measurement/
XCP
Calibration
Master
Slave
PC
Hardware*
EXE/DLL
Slave
HIL/SIL Systems
Figure 5:
XCP Slaves can be
Slave
used in many
different runtime
* Debug Interfaces, Memory Emulator ...
environments
16
1 Fundamentals of the XCP Protocol
How can algorithms be optimized using read and write access to the ECU and what bene
fits does this offer? To be able to modify individual parameters at runtime in the ECU, there
must be access to them. Not every type of memory permits this process. It is only possible
to perform a read and write access to memory addresses in RAM (intentionally excluding
the EEPROM here). The following is a brief summary of the differences between individual
memory technologies: knowledge of them is very important to understanding over the fur
ther course of this book.
Memory Fundamentals
Today, flash memories are usually integrated in the microcontroller chips for ECUs and are
used for longterm storage of code and data, even without power supply. The special aspect
of a flash memory is that read and write access to individual bytes is indeed possible at any
time, but writing of new contents can only be done blockwise, usually in rather large blocks.
Flash memories have a limited life, which is specified in terms of a maximum number of era
sure cycles (depending on the specific technology the maximum may be up to one million
cycles). This is also the maximum number of write cycles, because the memory must always
be erased as a block before it can be written again. The reason for this lies in the memory
structure: electrons are “pumped” via tunnel diodes. A bit is stored at a memory location as
follows: electrons must be transported into the memory location over an electrically insulating
layer. Once the electrons are then behind the insulating layer, they form an electric field with
their charge, which is interpreted as a 1 when reading the memory location. If there are no
electrons behind the layer, the cell information is interpreted as a 0. A 1 can indeed be set in
this way, but not a 0. Setting to 0 (= erasing the 1) is performed in a separate erasing routine,
in which electrons existing behind the insulating layer are discharged. However, for architec
tural reasons, such an erasing routine does not just act on single bytes, rather only on the
group or block level. Depending on the architecture, blocks of 128 or 256 bytes are usually used.
If one wishes to overwrite a byte within such a block, the entire block must first be erased.
Then the entire contents of the block can be written back.
When this erasing routine is repeated multiple times, the insulating layer (“Tunnel Oxide Film”)
can be damaged. This means that the electrons could slowly leak away, changing some of the
information from 1 to 0 over the course of time. Therefore, the number of allowable flash
cycles is severely limited in an ECU. In the production ECU, it is often only on the order of single
digit numbers. This restriction is monitored by the Flash Boot Loader, which uses a counter to
keep track of how many flash operations have already been executed. When the specified
number is exceeded, the Flash Boot Loader rejects another flash request.
A RAM (Random Access Memory) requires a permanent power supply; otherwise it loses its
contents. While flash memory serves the purpose of longterm storage of the application,
the RAM is used to buffer computed data and other temporary information. Shutting off
the power supply causes the RAM contents to be lost. In contrast to flash memory, it is easy
to read and write to RAM.
1 Fundamentals of the XCP Protocol
17
This fact is clear: if parameters need to be changed at runtime, it must be assured that they
are located in RAM. It is really very important to understand this circumstance. That is why
we will look at the execution of an application in the ECU based on the following example:
In the application, the y parameters are computed from the sensor values x.
// Pseudocode representation
a = 5;
b = 2;
y = a * x + b;
If the application is flashed in the ECU, the controller handles this code as follows after
booting: the values of the x parameters correspond to a sensor value. At some time point,
the application must therefore poll the sensor value and the value is then stored in a mem
ory location assigned to the x parameters. Since this value always needs to be rewritten at
runtime, the memory location can only lie in RAM.
The parameter y is computed. The values a and b, as factor and offset, are included as infor
mation in flash memory. They are stored as constants there. The value of y must also be
stored in RAM, because once again that is the only place where write access is pos sible. At
precisely which location in RAM the parameters x and y are located, or where a and b lie in
flash, is set in the compiler/linker run. This is where objects are allocated to unique addresses.
The relationship between object name, data type and address is documented in the linker
map file. The linkermap file is generated by the Linker run and can exist in different formats.
Common to all formats, however, is that they contain the object name and address at a
minimum.
In the example, if the offset b and factor a depend on the specific vehicle, the values of a and
b must be individually adapted to the specific conditions of the vehicle. This means that the
algorithm remains as it is, but the parameter values change from vehicle to vehicle.
In the normal operating mode of an ECU, the application runs from the flash memory. It
does not permit any write accesses to individual objects. This means that parameter values
which are located in the flash area cannot be modified at runtime. If a change to parameter
values should be possible during runtime, the parameters to be modified must lie in RAM
and not in flash. Now, how do the parameters and their initial values make their way into
RAM? How does one solve the problem of needing to modify more parameters than can be
simultaneously stored in RAM? These issues lead us to the topic of calibration concepts (see
chapter 3).
18
1 Fundamentals of the XCP Protocol
Summary of XCP fundamentals
Read and write accesses to memory contents are available with the mechanisms of the XCP
protocol. The accesses are made in an addressoriented way. Read access enables measure
ment of parameters from RAM, and write access enables calibration of the parameters in
RAM. XCP permits execution of the measurement synchronous to events in the ECU. This
ensures that the measured values correlate with one another. With every restart of a
measurement, the signals to be measured can be freely selected. For write access, the
parameters to be calibrated must be stored in RAM. This requires a calibration concept
This leads to two important questions:
> How does the user of the XCP protocol know the correct addresses of the measurement
and calibration parameters in RAM?
> What does the calibration concept look like?
The first question is answered in chapter 2 “ECUs description file A2L”. The topic of the cali
bration concept is addressed in chapter 3.
1.1 XCP Protocol Layer
19
1.1 XCP Protocol Layer
XCP data is exchanged between the Master and Slave in a messagebased way. The entire
“XCP message frame” is embedded in a frame of the transport layer (in the case of XCP on
Ethernet with UDP in a UDP packet). The frame consists of three parts: the XCP header, the
XCP packet and the XCP tail.
In the following figure, part of a message is shown in red. It is used to send the current XCP
frame. The XCP header and XCP tail depend on the transport protocol.
XCP Message (Frame)
XCP Header
XCP Packet
XCP Tail
PID FILL
DAQ
TIMESTAMP
DATA
Identification
Timestamp
Data
Figure 6:
Field
Field
Field
XCP packet
The XCP packet itself is independent of the transport protocol used. It always contains three
components: “Identification Field”, “Timestamp Field” and the current data field “Data
Field”. Each Identification Field begins with the Packet Identifier (PID), which identifies the
packet.
The following overview shows which PIDs have been defined:
PID for frames
PID for frames
from Master to Slave
from Slave to Master
0xFF
0xFF
RES
0xFE
ERR
CMD
....
0xFD
EV
0xC0
0xFC
SERV
0xBF
0xFB
absolute or
absolute or
relative
....
relative
ODT number
....
ODT number
for STIM
for DAQ
0x00
0x00
Figure 7: Overview of XCP Packet Identifier (PID)
20
1 Fundamentals of the XCP Protocol
Communication via the XCP packet is subdivided into one area for commands (CTO) and
one area for sending synchronous data (DTO).
XCP Master
XCP Driver
CTO
DTO
CMD
RES
ERR
EV
SERV
DAQ
STIM
Command / Response / Error /
DAQ
STIM
Event / Service Request Processor
Processor
Processor
Bypass
XCP Handler
PGM
CAL
DAQ
STIM
Resources
Figure 8:
XCP Slave
XCP communication
model with CTO/DTO
The acronyms used here stand for
CMD
Command Packet
sends commands
RES
Command Response Packet
positive response
ERR
Error
negative response
EV
Event Packet
asynchronous event
SERV
Service Request Packet
service request
DAQ
Data AcQuisition
send periodic measured values
STIM
Stimulation
periodic stimulation of the Slave
Commands are exchanged via CTOs (Command Transfer Objects). The Master initiates con
tact in this way, for example. The Slave must always respond to a CMD with RES or ERR.
The other CTO messages are sent asynchronously. The Data Transfer Objects (DTO) are
used to exchange synchronous measurement and stimulation data.
1.1 XCP Protocol Layer
21
1.1.1 Identification Field
XCP Packet
PID FILL
DAQ
TIMESTAMP
DATA
Identification Field
Figure 9:
Message identification
When messages are exchanged, both the Master and Slave must be able to determine which
message was sent by the other. This is accomplished in the identification field. That is why
each message begins with the Packet Identifier (PID).
In transmitting CTOs, the PID field is fully sufficient to identify a CMD, RES or other CTO
packet. In Figure 7, it can be seen that commands from the Master to the Slave utilize a PID
from 0xC0 to 0xFF. The XCP Slave responds or informs the Master with PIDs from 0xFC to
0xFF. This results in a unique allocation of the PIDs to the individually sent CTOs.
When DTOs are transmitted, other elements of the identification field are used (see chap
ter 1.3.4 “XCP Packet Addressing for DAQ and STIM”).
1.1.2 Timestamp
XCP Packet
PID FILL
DAQ
TIMESTAMP
DATA
Figure 10:
Timestamp
DTO packets use timestamps, but this is not possible in transmission of a CTO message. The
Slave uses the timestamp to supply time information with measured values. That is, the
Master not only has the measured value, but also the time point at which the measured
value was acquired. The amount of time it takes for the measured value to arrive at the
Master is no longer important, because the relationship between the measured value and
the time point comes directly from the Slave.
Transmission of a timestamp from the Slave is optional. This topic is discussed further in
ASAM XCP Part 2 Protocol Layer Specification.
22
1 Fundamentals of the XCP Protocol
1.1.3 Data Field
XCP Packet
PID FILL
DAQ
TIMESTAMP
DATA
Figure 11:
Data Field
Data field in the
XCP packet
Finally, the XCP packet also contains the data stored in the data field. In the case of CTO
packets, the data field consists of specific parameters for the different commands. DTO
packets contain the measured values from the Slave and when STIM data is sent the values
from the Master.
1.2 Exchange of CTOs
CTOs are used to transmit both commands from the Master to the Slave and responses
from the Slave to the Master.
1.2.1 XCP Command Structure
The Slave receives a command from the Master and must react to it with a positive or neg
ative response. The communication structure is always the same here:
Command (CMD):
Position
Type Description
0
BYTE
Command Packet Code CMD
1..MAX_CTO1
BYTE
Command specific Parameters
A unique number is assigned to each command. In addition, other specific parameters may
be sent with the command. The maximum number of parameters is defined as MAX_CTO1
here. MAX_CTO indicates the maximum length of the CTO packets in bytes.
Positive response:
Position
Type Description
0
BYTE
Command Positive Response Packet Code = RES 0xFF
1..MAX_CTO1
BYTE
Command specific Parameters
1.2 Exchange of CTOs
23
Negative response:
Position
Type Description
0
BYTE
Error Packet Code = 0xFE
1
BYTE
Error code
2..MAX_CTO1 BYTE
Command specific Parameters
Specific parameters can be transmitted as supplemental information with negative
responses as well and not just with positive responses. One example is when the connection
is made between Master and Slave. At the start of a communication between Master and
Slave, the Master sends a connect request to the Slave, which in turn must respond posi
tively to produce a continuous pointtopoint connection.
Master à Slave: Connect
Slave à Master: Positive Response
Connect command:
Position
Type Description
0
BYTE
Command Code = 0xFF
1
BYTE Mode
00 = Normal
01 = user defined
Mode 00 means that the Master wishes XCP communication with the Slave. If the Master
uses 0xFF 0x01 when making the connection, the Master is requesting XCP communication
with the Slave. Simultaneously, it informs the Slave that it should switch to a specific – user
defined – mode.
Positive response of the Slave:
Position
Type Description
0
BYTE
Packet ID: 0xFF
1
BYTE RESOURCE
2
BYTE COMM_MODE_BASIC
3
BYTE
MAX_CTO, Maximum CTO size [BYTE]
4
WORD
MAX_DTO, Maximum DTO size [BYTE]
6 BYTE
XCP Protocol Layer Version Number (most significant byte only)
7 BYTE
XCP Transport Layer Version Number (most significant byte only)
The positive response of the Slave can assume a somewhat more extensive form. The Slave
already sends communicationspecific information to the Master when making the connec
tion. RESOURCE, for example, is information that the Slave gives on whether it supports
such features as page switching or whether flashing over XCP is possible. With MAX_DTO,
the Slave informs the Master of the maximum packet length it supports for transfer of the
measured values, etc. You will find details on the parameters in ASAM XCP Part 2 Protocol
Layer Specification.
24
1 Fundamentals of the XCP Protocol
XCP permits three different modes for exchanging commands and reactions between
Master and Slave: Standard, Block and Interleaved mode.
Standard Mode
Block Mode
Interleaved Mode
Master
Slave
Master
Slave
Master
Slave
Request k
Request k
Request k
Part1
Part2
MIN_ST
Request k+1
Part3
MAX_BS
Response k
Response k
Request k+1
Response k
Request k+1
Response k+1
Response k+1
Part1
Response k+1
Part2
Part3
Time
Time
Time
Figure 12: The three modes of the XCP protocol: Standard, Block and Interleaved mode
In the standard communication model, each request to a Slave is followed by a single
response. Except with XCP on CAN, it is not permitted for multiple Slaves to react to a com
mand from the Master. Therefore, each XCP message can always be traced back to a unique
Slave. This mode is the standard case in communication.
The block transfer mode is optional and saves time in large data transfers (e.g. upload or
download operations). Nonetheless, performance issues must be considered in this mode in
the direction of the Slave. Therefore, minimum times between two commands (MIN_ST)
must be maintained and the total number of commands must be limited to an upper limit
MAX_BS. Optionally, the Master can read out these communication settings from the Slave
with GET_COMM_MODE_INFO. The aforementioned limitations do not need to be observed
in block transfer mode in the direction of the Master, because performance of the PC nearly
always suffices to accept the data from a microcontroller.
The interleaved mode is also provided for performance reasons. But this method is also
optional and – in contrast to block transfer mode – it has no relevance in practice.
1.2 Exchange of CTOs
25
1.2.2 CMD
XCP CTO Packet
PID
DATA
Data Field
Identification Field
Timestamp Field
empty for CTO
Figure 13: Overview of the CTO packet structure
The Master sends a general request to the Slave over CMD. The PID (Packet Identifier) field
contains the identification number of the command. The additional specific parameters are
transported in the data field. Then the Master waits for a reaction of the Slave in the form
of a RESponse or an ERRor.
XCP is also very scalable in its implementation, so it is not necessary to implement every
command. In the A2L file, the available CMDs are listed in what is known as the XCP
IF_DATA. If there is a discrepancy between the definition in the A2L file and the implemen
tation in the Slave, the Master can determine, based on the Slave’s reaction, that the Slave
does not even support the command. If the Master sends a command that is not imple
mented in the Slave, the Slave must acknowledge with ERR_CMD_UNKNOWN and no fur
ther activities are initiated in the Slave. This lets the Master know quickly that an optional
command has not been implemented in the Slave.
Some other parameters are included in the commands as well. Please take the precise
details from the protocol layer specification in document ASAM XCP Part 2.
The commands are organized in groups: Standard, Calibration, Page, Programming and
DAQ measurement commands. If a group is not needed at all, its commands do not need to
be implemented. If the group is necessary, certain commands must always be available in
the Slave, while others from the group are optional.
The following overview serves as an example. The SET_CAL_PAGE and GET_CAL_PAGE
commands in the page switching group are identified as not optional. This means that in an
XCP Slave that supports page switching at least these two commands must be imple
mented. If page switching support is unnecessary in the Slave, these commands do not need
to be implemented. The same applies to other commands.
26
1 Fundamentals of the XCP Protocol
Standard commands:
Command
PID Optional
CONNECT
0xFF No
DISCONNECT
0xFE No
GET_STATUS
0xFD No
SYNCH
0xFC No
GET_COMM_MODE_INFO 0xFB Yes
GET_ID
0xFA Yes
SET_REQUEST
0xF9 Yes
GET_SEED
0xF8 Yes
UNLOCK
0xF7 Yes
SET_MTA
0xF6 Yes
UPLOAD
0xF5 Yes
SHORT_UPLOAD
0xF4 Yes
BUILD_CHECKSUM
0xF3 Yes
TRANSPORT_LAYER_CMD 0xF2 Yes
USER_CMD
0xF1 Yes
Calibration commands:
Command
PID Optional
DOWNLOAD
0xF0 No
DOWNLOAD_NEXT
0xEF Yes
DOWNLOAD_MAX
0xEE Yes
SHORT_DOWNLOAD
0xED Yes
MODIFY_BITS
0xEC Yes
Standard commands:
Command
PID Optional
SET_CAL_PAGE
0xEB No
GET_CAL_PAGE
0xEA No
GET_PAG_PROCESSOR_INFO 0xE9 Yes
GET_SEGMENT_INFO
0xE8 Yes
GET_PAGE_INFO
0xE7 Yes
SET_SEGMENT_MODE
0xE6 Yes
GET_SEGMENT_MODE
0xE5 Yes
COPY_CAL_PAGE
0xE4 Yes
1.2 Exchange of CTOs
27
Periodic data exchange – basics:
Command
PID Optional
SET_DAQ_PTR
0xE2 No
WRITE_DAQ
0xE1 No
SET_DAQ_LIST_MODE
0xE0 No
START_STOP_DAQ_LIST
0xDE No
START_STOP_SYNCH
0xDD No
WRITE_DAQ_MULTIPLE
0xC7 Yes
READ_DAQ
0xDB Yes
GET_DAQ_CLOCK
0xDC Yes
GET_DAQ_PROCESSOR_INFO 0xDA Yes
GET_DAQ_RESOLUTION_INFO 0xD9
Yes
GET_DAQ_LIST_INFO
0xD8 Yes
GET_DAQ_EVENT_INFO
0xD7 Yes
Periodic data exchange – static configuration:
Command
PID Optional
CLEAR_DAQ_LIST
0xE3 No
GET_DAQ_LIST_INFO
0xD8 Yes
Periodic data exchange – dynamic configuration:
Command
PID Optional
FREE_DAQ
0xD6 Yes
ALLOC_DAQ
0xD5 Yes
ALLOC_ODT
0xD4 Yes
ALLOC_ODT_ENTRY
0xD3 Yes
28
1 Fundamentals of the XCP Protocol
Flash programming:
Command
PID Optional
PROGRAM_START
0xD2 No
PROGRAM_CLEAR
0xD1 No
PROGRAM
0xD0 No
PROGRAM_RESET
0xCF No
GET_PGM_PROCESSOR_INFO 0xCE
Yes
GET_SECTOR_INFO
0xCD Yes
PROGRAM_PREPARE
0xCC Yes
PROGRAM_FORMAT
0xCB Yes
PROGRAM_NEXT
0xCA Yes
PROGRAM_MAX
0xC9 Yes
PROGRAM_VERIFY
0xC8 Yes
1.2.3 RES
If the Slave is able to successfully comply with a Master’s request, it gives a positive acknowl
edge with RES.
Position
Type Description
0
BYTE
Packet Identifier = RES 0xFF
1..MAX_CTO1
BYTE
Command response data
You will find more detailed information on the parameters in ASAM XCP Part 2 Protocol
Layer Specification.
1.2.4 ERR
If the request from the Master is unusable, it responds with the error message ERR and an
error code.
Position
Type Description
0
BYTE
Packet Identifier = ERR 0xFE
1
BYTE
Error code
2..MAX_CTO1 BYTE
Optional error information data
You will find a list of possible error codes in ASAM XCP Part 2 Protocol Layer Specification.
1.2 Exchange of CTOs
29
1.2.5 EV
If the Slave wishes to inform the Master of an asynchronous event, an EV can be sent to do
this. Its implementation is optional.
Position
Type Description
0
BYTE
Packet Identifier = EV 0xFD
1
BYTE
Event code
2..MAX_CTO1 BYTE
Optional event information data
You will find more detailed information on the parameters in ASAM XCP Part 2 Protocol
Layer Specification.
Events will be discussed much more in relation to measurements and stimulation. This has
nothing to do with the action of the XCP Slave that initiates sending of an EVENT. Rather it
involves the Slave reporting a disturbance such as the failure of a specific functionality.
1.2.6 SERV
The Slave can use this mechanism to request that the Master execute a service.
Position
Type Description
0
BYTE
Packet Identifier = SERV 0xFC
1
BYTE
Service request code
2..MAX_CTO1 BYTE
Optional service request data
You will find the Service Request Code table in ASAM XCP Part 2 Protocol Layer
Specification.
1.2.7 Calibrating Parameters in the Slave
To change a parameter in an XCP Slave, the XCP Master must send the parameter’s loca
tion as well as the value itself to the Slave.
XCP always defines addresses with five bytes: four for the actual address and one byte for
the address extension. Based on a CAN transmission, only seven useful bytes are available
for XCP messages. For example, if the calibrator sets a 4byte value and wants to send both
pieces of information in one CAN message, there is insufficient space to do this. Since a
total of nine bytes are needed to transmit the address and the new value, the change can
not be transmitted in one CAN message (seven useful bytes). The calibration request is
therefore made with two messages from Master to Slave. The Slave must acknowledge
both messages and in sum four messages are exchanged.
30
1 Fundamentals of the XCP Protocol
The following figure shows the communication between Master and Slave, which is neces
sary to set a parameter value. The actual message is located in the line with the envelope
symbol. The interpretation of the message is shown by “expanding” it with the mouse.
Figure 14: Trace example from a calibration process in CANape
In the first message of the Master (highlighted in blue in Figure 14), the Master sends the
command SET_MTA to the Slave with the address to which a new value should be written.
In the second message, the Slave gives a positive acknowledge to the command with
Ok:SET_MTA.
The third message DOWNLOAD transmits the hex value as well as the valid number of
bytes. In this example, the valid number of bytes is four, because it is a float value. The Slave
gives another positive acknowledge in the fourth message.
This completes the current calibration process. In the Trace display, you can recognize a ter
minating SHORT_UPLOAD – a special aspect of CANape, the measurement and calibration
tool from Vector. To make sure that the calibration was performed successfully, the value is
read out again after the process and the display is updated with the readout value. This lets
the user directly recognize whether the calibration command was implemented. This com
mand also gets a positive acknowledge with Ok:SHORT_UPLOAD.
When the parameter changes in the ECU’s RAM, the application processes the new value. A
reboot of the ECU, however, would lead to erasure of the value and overwriting of the value
in RAM with the original value from the flash (see chapter 3 “Calibration Concepts”). So,
how can the modified parameter set be permanently saved?
1.2 Exchange of CTOs
31
Essentially, there are two possibilities:
A) Save the parameters in the ECU
The changed data in RAM could for example be saved in the ECU’s EEPROM: either auto
matically when ramping down the ECU, or manually by the user. A prerequisite is that the
data can be stored in a nonvolatile memory of the Slave. In an ECU, this would be the
EEPROM or flash. ECUs with thousands of parameters, however, are seldom able to provide
so much unused EEPROM memory space, so this method is rare.
Another possibility is to write the RAM parameters back into the ECU’s flash memory. This
method is relatively complex. A flash memory must first be erased before it can be rewrit
ten. This, in turn, can only be done as a block. Consequently, it is not simply a matter of writ
ing back individual bytes. You will find more on this topic in chapter 3 “Calibration
Concepts”.
B) Save the parameters in the form of a file on the PC
It is much more common to store the parameters on the PC. All parameters – or subsets of
them – are stored in the form of a file. Different formats are available for this; the simplest
case is that of an ASCII text file, which only contains the name of the object and its value.
Other formats also permit saving other information, such as findings about the maturity
level of the parameter of the history of revisions.
Scenario: After finishing his or her work, the calibrator wishes to enjoy a free evening. So, the
calibrator saves the executed changes in the ECU’s RAM in the form of a parameter set file
on a PC. The next day, the calibrator wants to continue working where he or she left off. The
calibrator starts the ECU. Upon booting, the parameters are initialized in RAM. However,
the ECU does this using values stored in flash. This means that the changes of the previous
day are no longer available in the ECU. To now continue where work was left off on the pre
vious day, the calibrator transfers the contents of the parameter set file to the ECU’s RAM
by XCP using the DOWNLOAD command.
Figure 15: Transfer of a parameter set file to an ECU’s RAM
32
1 Fundamentals of the XCP Protocol
Saving parameter set file in hex files and flashing
Flashing an ECU is another way to change the parameters in flash. They are then written to
RAM as new parameters when the ECU is booted. A parameter set file can also be trans
ferred to a C or H file and be made into the new flash file with another compiler/linker run.
However, depending on the parameters of the code, the process of generating a flashable
hex file could take a considerable amount of time. In addition, the calibrator might not have
any ECU source code – depending on the work process. That would prevent this method
from being available to the calibrator.
As an alternative, the calibrator can copy the parameter set file into the existing flash file.
Figure 16: Hex window
In the flash file, there is a hex file that contains both the addresses and the values. Now a
parameter file can be copied to a hex file. To do this, CANape takes the address and the
value from the parameter set file and updates the parameter value at the relevant location
in the hex file. This results in a new hex file, which contains the changed parameter values.
However, this Hex file must now possibly run through further process steps to obtain a flash
able file. One recurring problem here is the checksums, which the ECU checks to determine
whether it received the data correctly. If the flashable file exists, it can be flashed in the ECU
and after the reboot the new parameter values are available in the ECU.
1.3 Exchanging DTOs – Synchronous Data Exchange
As depicted in Figure 8, DTOs (Data Transfer Objects) are available for exchanging synchro
nous measurement and calibration data. Data from the Slave are sent to the Master by
DAQ – synchronous to internal events. This communication is subdivided into two phases:
In an initialization phase, the Master communicates to the Slave which data the Slave
should send for different events. After this phase, the Master initiates the measurement in
the Slave and the actual measurement phase begins. From this point in time, the Slave
sends the desired data to the Master, which only listens until it sends a “measurement stop”
to the Slave. Triggering of measurement data acquisition and transmission is controlled by
events in the ECU.
1.3 Exchanging DTOs – Synchronous Data Exchange
33
The Master sends data to the Slave by STIM. This communication also consists of two
phases:
In the initialization phase, the Master communicates to the Slave which data it will send to
the Slave. After this phase, the Master sends the data to the Slave and the STIM processor
saves the data. As soon as a related STIM event is triggered in the Slave, the data is trans
ferred to the application memory.
1.3.1 Measurement Methods: Polling versus DAQ
Before explaining how eventsynchronous, correlated data is measured from a Slave, here is
a brief description of another measurement method known as Polling. It is not based on
DTOs, but on CTOs instead. Actually, this topic should be explained in a separate chapter,
but a description of polling lets us derive, in a very elegant way, the necessity of DTObased
measurement, so a minor side discussion at this point makes sense.
The Master can use the SHORT_UPLOAD command to request the value of a measurement
para meter from the Slave. This is referred to as polling. This is the simplest case of a
measure ment: sending the measured value of a measurement parameter at the time at
which the SHORT_UPLOAD command has been received and executed.
In the following example, the measurement parameter “Triangle” is measured from the
Slave:
Figure 17:
Address information
of the parameter
“Triangle” from the
A2L file
The address 0x60483 is expressed as an address with five bytes in the CAN frame: one byte
for the address extension and four bytes for the actual address.
34
1 Fundamentals of the XCP Protocol
Figure 18: Polling communication in the CANape Trace window
The XCP specification sets a requirement for polling: that the value of each measurement
parameter must be polled individually. For each value to be measured via polling, two mes
sages must go over the bus: the Master’s request to the Slave and the Slave’s response to
the Master.
Besides this additional bus load, there is another disadvantage of the polling method: When
polling multiple data values, the user normally wants the data to correlate to one another.
However, multiple values that are measured sequentially with polling do not necessarily
stand in correlation to one another, i.e. they might not originate from the same ECU com
puting cycle.
This limits the suitability of polling for measurement, because it produces unnecessarily high
data traffic and the measured values are not evaluated in relation to the process flows in
the ECU.
So, an optimized measurement must solve two tasks:
> Bandwidth optimization during the measurement
> Assurance of data correlation
This task is handled by the already mentioned DAQ method. DAQ stands for Data Acquisi
tion and it is implemented by sending DTOs (Data Transfer Objects) from the Slave to the
Master.
1.3.2 DAQ Measurement Method
The DAQ method solves the two problems of polling as follows:
> The correlation of measured values is achieved by coupling the acquisition of measured
values to the events in the ECU. The measured values are not acquired and transferred
until it has been assured that all computations have been completed.
> To reduce bus load, the measurement process is subdivided into two phases: In a configu
ration phase, the Master communicates which values it is interested in to the Slave and
the second phase just involves transferring the measured values of the Slave to the
Master.
1.3 Exchanging DTOs – Synchronous Data Exchange
35
How can the acquisition of measured values now be coupled to processes in the ECU? Figure
19 shows the relationship between calculation cycles in the ECU and the changes in para
meters X and Y.
Calculation
Calculation
Calculation
cycle n
cycle n+1
cycle n+2
time
10
8
6
X 4 2 0
10
8
6
Y 4 2 0
E1
E1
E1
Read sensor X
Calculate Y = X
Figure 19:
Events in the ECU
Let’s have a look at the sequence in the ECU: When event E1 (= end of computation cycle) is
reached, then all parameters have been acquired and calculations have been made. This
means that all values must match one another and correlate at this time point. This means
that we use an eventsynchronous measurement method. This is precisely what is imple
mented with the help of the DAQ mechanism: When the algorithm in the Slave reaches the
“Computational cycle completed” event, the XCP Slave collects the values of the measure
ment parameters, saves them in a buffer and sends them to the Master. This assumes that
the Slave knows which parameters should be measured for which event.
An event does not absolutely have to be a cyclic, timeequidistant event, rather in the case
of an engine controller, for example, it might be anglesynchronous. This makes the time
interval between two events dependent on the engine rpm. A singular event, such as activa
tion of a switch by the driver, is also an event that is not by any means equidistant in time.
The user selects the signals. Besides the actual measurement object, the user must select
the underlying event for the measurement parameters. The events as well as the possible
assignments of the measurement objects to the events must be stored in the A2L file.
Figure 20:
Event definition
in an A2L
36
1 Fundamentals of the XCP Protocol
In the normal case, it does not make any sense to be able to simultaneously assign a mea
sured value to multiple events. Generally, a parameter is only modified within a single cycle
(e.g. only at 10ms intervals) and not in multiple cycles (e.g. at 10ms and 100ms
intervals).
Figure 21:
Allocation of
“Triangle” to possible
events in the A2L
Figure 21 shows that the “Triangle” parameter can in principle be measured with the 1 ms,
10 ms and 100 ms events. The default setting is 10 ms.
Measurement parameters are allocated to events in the ECU during measurement configu
ration by the user.
Figure 22:
Selecting events
(measurement mode)
for each measurement
parameter
After configuring the measured signals, the user starts the measurement. The XCP Master
lists the desired measurement parameters in what are known as DAQ lists. In these lists, the
measured signals are each allocated to selected events. This configuration information is
sent to the Slave before the actual start of measurement. Then the Slave knows which
addresses it should read out and transmit when an event occurs. This distribution of the
measurement into a configuration phase and a measurement phase was already mentioned
at the very beginning of this chapter.
This solves both problems that occur in polling: bandwidth is used optimally, because the
Master no longer needs to poll each value individually during the measurement and the
measured values correlate with one another.
1.3 Exchanging DTOs – Synchronous Data Exchange
37
Figure 23: Excerpt from the CANape Trace window of a DAQ measurement
Figure 23 illustrates an example of commandresponse communication (color highlighting)
between Master and Slave (overall it is significantly more extensive and is only shown in part
here for reasons of space). This involves transmitting the DAQ configuration to the Slave.
Afterwards, the measurement start is triggered and the Slave sends the requested values
while the Master just listens.
Until now, the selection of a signal was described based on its name and allocation to a
measurement event. But how exactly is the configuration transferred to the XCP Slave?
Let us look at the problem from the perspective of memory structure in the ECU: The user
has selected signals and wishes to measure them. So that sending a signal value does not
require the use of an entire message, the signals from the Slave are combined into message
packets. The Slave does not create this definition of the combination independently, or else
the Master would not be able to interpret the data when it received the messages. There
fore, the Slave receives an instruction from the Master describing how it should distribute
the values to the messages.
The sequence in which the Slave should assemble the bytes into messages is defined in what
are known as Object Description Tables (ODTs). The address and object length are impor
tant to uniquely identify a measurement object. An ODT provides the allocations of RAM
contents from the Slave to assemble a message on the bus. According to the communica
tion model, this message is transmitted as a DAQ DTO (Data Transfer Object).
38
1 Fundamentals of the XCP Protocol
RAM Cells
ODT
0
address, length
1
address, length
2
address, length
3
address, length
...
PID 0
1
2
3 ...
Figure 24:
ODT: Allocation of RAM
addresses to DAQ DTO
Stated more precisely, an entry in an ODT list references a memory area in RAM by the
address and length of the object.
After receiving the measurement start command, at some point an event occurs that is
associated with a measurement. The XCP Slave begins to acquire the data. It combines the
individual objects into packets and sends them on the bus. The Master reads the bus mes
sage and can interpret the individual data, because it has defined the allocation of individ
ual objects to packets itself and therefore it knows their relationships.
However, each packet has a maximum number of useful bytes, which depends on the trans
port medium that is used. In the case of CAN, this amounts to seven bytes. If more data
needs to be measured, an ODT is no longer sufficient. If two or more ODTs need to be used
to transmit the measured values, then the Slave must be able to copy the data into the cor
rect ODT and the Master must be able to uniquely identify the received ODTs. If multiple
measurement intervals of the ECU are used, the relationship between ODT and measure
ment interval must also be uniquely identifiable.
1.3 Exchanging DTOs – Synchronous Data Exchange
39
The ODTs are combined into DAQ lists in the XCP protocol. Each DAQ list contains a num
ber of ODTs and is assigned to an event.
ODT #2 0 address, length
1 address, length
ODT #1 0 address, length
2 address, length
1 address, length
ODT #0 0 address, length
3 address, length
2 address, length
1 address, length ...
PID=2 0
1
2
3
...
3 address, length
2 address, length
...
PID=1 0
1
2
3
...
3 address, length
...
PID=0 0
1
2
3
...
Figure 25:
DAQ list with three ODTs
For example, if the user uses two measurement intervals (= two different events in the
ECU), then two DAQ lists are used as well. One DAQ list is needed per event used. Each DAQ
list contains the entries related to the ODTs and each ODT contains references to the values
in the RAM cells.
It is also possible for the Slave to transfer time information. A DAQ list represents the val
ues belonging to a specific time event. Before these values in the Slave are recorded, the
point in time of the event is noted and transferred within the first ODT. The timestamp is
implemented using a counter. The time interval at which the counter is incremented is spec
ified in the A2L.
DAQ lists are subdivided into the types: static, predefined and dynamic.
40
1 Fundamentals of the XCP Protocol
Static DAQ lists:
If the DAQ lists and ODT tables are permanently defined in the ECU, as is familiar from CCP,
they are referred to as static DAQ lists. There is no definition of which measurement para
meters exist in the ODT lists, rather only the framework that can be filled (in contrast to
this, see predefined DAQ lists).
In static DAQ lists, the definitions are set in the ECU code and are described in the A2L.
Figure 26 shows an excerpt of an A2L, in which static DAQ lists are defined:
Figure 26:
Static DAQ lists
In the above example, there is a DAQ list with the number 0, which is allocated to a 10ms
event and can carry a maximum of two ODTs. The DAQ list with the number 1 has four ODTs
and is linked to the 100 ms event.
The A2L matches the contents of the ECU. In the case of static DAQ lists, the number of
DAQ lists and the ODT lists they each contain are defined with the download of the applica
tion into the ECU. If the user now attempts to measure more signals with an event than fit
in the allocated DAQ list, the Slave in the ECU will not be able to fulfill the requirements and
the configuration attempt is terminated with an error. It does not matter that the other
DAQ list is still fully available and therefore actually still has transmission capacity.
Predefined DAQ lists:
Entirely predefined DAQ lists can also be set up in the ECU. However, this method is practi
cally never used in ECUs due to the lack of flexibility for the user. It is different for analog
measurement systems which transmit their data by XCP: Flexibility is unnecessary here,
since the physical structure of the measurement system remains the same over its life.
1.3 Exchanging DTOs – Synchronous Data Exchange
41
Dynamic DAQ lists:
A special aspect of the XCP protocol are the dynamic DAQ lists. It is not the absolute param
eters of the DAQ and ODT lists that are permanently defined in the ECU code here, but just
the parameters of the memory area that can be used for the DAQ lists. The advantage is
that the measurement tool has more latitude in putting together the DAQ lists and it can
manage the structure of the DAQ lists dynamically.
Various functions especially designed for this dynamic management are available in XCP
such as ALLOC_ODT which the Master can use to define the structure of a DAQ list in the
Slave.
MIN_DAQ + DAQ_COUNT
DAQ1
DAQ0
ALLOC_DAQ
ALLOC_ODT_ENTRY
ODT_ENTERIES_COUNT
T
OC_OD
ALL
GRANULARITY_ODT_ENTRY_SIZE_DAQ
Figure 27:
ODT_COUNT
Dynamic DAQ lists
In putting together the DAQ lists, the Master must be able to distinguish whether dynamic
or static DAQ lists are being used, how the parameters and structures of the DAQ lists look,
etc.
42
1 Fundamentals of the XCP Protocol
1.3.3 STIM Calibration Method
The XCP calibration method was already introduced in the chapter about exchanging CTOs.
This type of calibration exists in every XCP driver and forms the basis for calibrating objects
in the ECU. However, no synchronization exists between sending a calibration command and
an event in the ECU.
In contrast to this, the use of STIM is not based on exchanging CTOs, rather on the use of
DTOs with communication that is synchronized to an event in the Slave. The Master must
therefore know to which events in the Slave it can even synchronize at all. This information
must also exist in the A2L.
Figure 28: Event for DAQ and STIM
If the Master sends data to the Slave by STIM, the XCP Slave must be informed of the loca
tion in the packets at which the calibration parameters can be found. The same mechanisms
are used here as are used for the DAQ lists.
1.3 Exchanging DTOs – Synchronous Data Exchange
43
1.3.4 XCP Packet Addressing for DAQ and STIM
Addressing of the XCP packets was already discussed at the beginning of this chapter. Now
that the concepts of DAQ, ODT and STIM have been introduced, XCP packet addressing will
be presented in greater detail.
During transmission of CTOs, the use of a PID is fully sufficient to uniquely identify a packet;
however, this is no longer sufficient for transmitting measured values. The following figure
offers an overview of the possible addressing that could occur with the DTOs:
XCP DTO Packet
Identification Field
Timestamp Field
Data Field
PID
PID DAQ
TS
PID
DAQ
TS
Figure 29:
PID FILL
DAQ
TIMESTAMP
DATA
Structure of the
XCP packet for
DTO transmissions
Transmission type: “absolute ODT numbers”
Absolute means that the ODT numbers are unique throughout the entire communication –
i.e. across all DAQ lists. In turn, this means that the use of absolute ODT numbers assumes
a transformation step that utilizes a socalled “FIRST_PID for the DAQ list.
If a DAQ list starts with the PID j, then the PID of the first packet has the value j, the second
packet has the PID value j + 1, the third packet has the PID value j + 2, etc. Naturally, the
Slave must ensure here that the sum of FIRST_PID + relative ODT number remains below
the PID of the next DAQ list.
DAQlist: 0
≤ PID ≤ k
DAQlist: k + 1 ≤ PID ≤ m
DAQlist: m + 1 ≤ PID ≤ n
etc.
44
1 Fundamentals of the XCP Protocol
In this case, the identification field is very simple:
Identification Field
PID
Figure 30:
absolute ODT number
Identification field with absolute
ODT numbers
Transmission type: “relative ODT numbers and absolute DAQ lists numbers”
In this case, both the DAQ lists number and the ODT number can be transmitted in the Iden
tification Field. However, there is still space left over in the number of bytes that is available
for the information:
Identification Field
PID DAQ
absolute DAQ list number
Figure 31:
relative ODT number
ID field with relative ODT and absolute
DAQ numbers (one byte)
In the figure, one byte is available for the DAQ number and one byte for the ODT number.
The maximum number of DAQ lists can be transmitted using two bytes:
Identification Field
PID
DAQ
absolute DAQ list number
Figure 32:
relative ODT number
ID field with relative ODT and absolute
DAQ numbers (two bytes)
1.3 Exchanging DTOs – Synchronous Data Exchange
45
If it is not possible to send three bytes, it is also possible to work with four bytes by using a
fill byte:
Identification Field
PID FILL
DAQ
absolute DAQ list number
for alignement
Figure 33:
ID field with relative ODT and
relative ODT number
absolute DAQ numbers as well as
fill byte (total of four bytes)
How does the XCP Master now learn which method the Slave is using? First, by the entry in
the A2L and second by the request to the Slave to determine which communication version
it has implemented.
The response to the GET_DAQ_PROCESSOR_INFO request also sets the DAQ_KEY_BYTE
that the Slave uses to inform the Master which transmission type is being used. If not only
DAQ is being used, but also STIM, the Master must use the same method for STIM that the
Slave uses for DAQ.
1.3.5 Bypassing = DAQ + STIM
Bypassing can be implemented by joint use of DAQ and STIM (see Figure 8) and it repre
sents a special form of a rapid prototyping solution. For a deeper understanding, however,
further details are necessary, so this method is not explained until chapter 4.5 “Bypassing”.
1.3.6. Time Correlation and Synchronization
Various mechanisms are available to the Master for correlating the timestamp of the mea
surement data of a Slave to the timestamps of other measurement data. In the simplest
form of a Slave implementation, the Slave features a clock and can access its value at any
time. The DAQ timestamps sent by the XCP Slave are based on this clock. Here, the Slave
transfers the time information in the first ODT of each DAQ event. The Slave retrieves the
timestamp at the point in time at which the event was initiated and at which it copies the
measurement data from RAM.
The correlation of this clock to other clocks is unknown to the Master, as the DAQ messages
require an undefined amount of time to reach the Master from the Slave. The clocks can be
correlated using the GET_DAQ_CLOCK command. Before the start of measurement, and
usually at regular intervals, the Master sends the GET_DAQ_CLOCK command and the
46
1 Fundamentals of the XCP Protocol
Slave responds with the current value of the Slave clock. Since the Master knows the point
in time at which it sent the command, it can calculate a time offset between the Master
clock and the Slave clock using the timestamp of the Slave and the point in time the com
mand was sent.
Naturally, this method is also afflicted with inaccuracies if the run time of the GET_DAQ_CLOCK
command is not precisely defined or the point in time at which the clocks are read in the
Master and Slave cannot be determined precisely when sending/receiving the command.
This is why version 1.3 of the XCP specification provides improved methods enabling correla
tion of the Master and Slave clocks with a precision of just a few microseconds.
1.3.6.1 Multicast
For better correlation of the clocks of multiple Slaves to one another, the Master reads the
clocks of multiple Slaves at the same time. For this purpose, the Master sends a command
to all Slaves which are accessible using the same transport medium. Each Slave records the
point in time at which it receives the command and transfers the value to the Master. To
achieve maximum precision, two requirements must be fulfilled to the greatest degree
possible:
On the one hand, the Slave implementation should ensure (as in the past) that the record
ing of the timestamp is initiated as soon as possible upon receipt of the command. On the
other hand, the latency times between the Slaves and the Master should be the same to the
greatest degree possible.
The GET_DAQ_CLOCK_MULTICAST command is available for this purpose. The Slave
responds with an EV_TIME_SYNC message, in which the timestamp is transferred.
XCP Slave
XCP Master
XCP Slave Clock
free running
GET_DAQ_CLOCK_MULTICAST
EV_TIME_SYNC
GET_DAQ_CLOCK_MULTICAST
EV_TIME_SYNC
Figure 34:
t
XCP Slave with
free-running clock
1.3 Exchanging DTOs – Synchronous Data Exchange
47
1.3.6.2. Grandmaster Clock
A further solution involves the time of the Slave already being synchronized/coordinated
with another clock, the socalled grandmaster clock.
First, an explanation of the terms “synchronized” and “coordinated”:
Stated simply, two clocks are synchronized with one another if they supply the identical
timestamp when they are read at the same time.
In contrast, clocks which are coordinated to one another do not necessarily need to sup
ply the same timestamp. In both clocks, 1 second is exactly the same length.
IEEE 1588 with PTP (Precision Time Protocol) is used. In the first step, the XCP Master must
know whether the Slave is linked to an external clock. As there can be more than one grand
master clock in an overall system, information on the exact clock to which the Slave is linked
must be available to the XCP Master.
XCP Slave
XCP Master
XCP Slave Clock
synchronized to a
Grandmaster Clock
Grandmaster Clock
e.g.
IEEE 1588
GET_DAQ_CLOCK_MULTICAST
EV_TIME_SYNC
GET_DAQ_CLOCK_MULTICAST
EV_TIME_SYNC
t
Figure 35: The clock of the XCP Slave is synchronized with the grandmaster clock
48
1 Fundamentals of the XCP Protocol
The XCP standard supports additional scenarios which can only briefly be sketched out here
briefly. Further details can be found in the XCP specifications.
> Should it be possible to coordinate the XCP Slave clock with the external clock, but
not synchronize them, there will be an offset between the grandmaster clock and
the Slave clock. The XCP Master can request the details from the Slave using the TIME_
CORRELATION_PROPERTIES command.
> The freerunning clock of the Slave cannot be synchronized with a grandmaster clock, but
there is another clock in the Slave, e.g. a clock synchronized with the grandmaster clock in
the Ethernet PHY of the Slave. If the Master receives both times at the same point in time,
it can correlate the DAQ timestamp of the freerunning clock with the grandmaster clock
and its own time domain.
> Another scenario arises when there is a freerunning clock of the XCP Slave and an ECU
clock and the DAQ timestamps originate from the ECU clock. This is the case when an
external XCP Slave, such as the VX1000 measurement and calibration hardware is used
from Vector, is used.
> If all of the sketched solutions are combined, a total of three different clocks are involved:
the freerunning Slave clock, a clock which is synchronized with a grandmaster clock and
the ECU clock.
> In the last scenario, there is no Slave clock, but there is an ECU clock which is synchronized
with a grandmaster clock.
Synchronization between the DAQ timestamps and the Master domain time can be realized
for all scenarios in the Master using the XCP mechanisms.
1.4 XCP Transport Layers
49
1.4 XCP Transport Layers
A main requirement in designing the XCP protocol was that it must support different trans
port layers. At the time this document was defined, the following layers had been defined:
XCP on CAN, FlexRay, Ethernet, SxI and USB. The bus systems CAN, LIN and FlexRay are
explained on the Vector ELearning platform, as well as an introduction to AUTOSAR. For
details see the website www.vectorelearning.com.
1.4.1 CAN
XCP was developed as a successor protocol of the CAN Calibration Protocols (CCP) and
must absolutely satisfy the requirements of the CAN bus. The communication over the CAN
bus is defined by the associated description file. Usually the DBC format is used, but in some
isolated cases the AUTOSAR format ARXML is being used too.
A CAN message is identified by a unique CAN identifier. The communication matrix is defined
in the description file: Who sends which message and how are the eight useful bytes of the
CAN bus being used? The following figure illustrates the process:
Data
CAN
CAN
CAN
CAN
Frame
Node A
Node B
Node C
Node D
ID=0x12
Sender
Receiver
ID=0x34
Sender
Receiver
Receiver
ID=0x52
Receiver
Sender
ID=0x67
Receiver
Receiver
Sender
Receiver
ID=0xB4
Receiver
Sender
Figure 36:
Definition of which
ID=0x3A5
Sender
Receiver
Receiver
Receiver
bus nodes send which
messages
The message with ID 0x12 is sent by CAN node A and all other nodes on the bus receive this
message. In the framework of acceptance testing, CAN nodes C and D conclude that they
do not need the message and they reject it. CAN node B, on the other hand, determines that
its higherlevel layers need the message and they provide them via the Rx buffer. The CAN
nodes are interlinked as follows:
50
1 Fundamentals of the XCP Protocol
CAN Node A
CAN Node B
Host
Host
CAN Interface
CAN Interface
Tx
Rx
Tx
Rx
Buffer
Buffer
Buffer
Buffer
Acceptance
Acceptance
Test
Test
Send
Receive
Send
Receive
CAN
Receive
Send
Receive
Send
Acceptance
Acceptance
Test
Test
Rx
Tx
Rx
Tx
Buffer
Buffer
Buffer
Buffer
CAN Interface
CAN Interface
Host
Host
Figure 37:
CAN Node C
CAN Node D
Representation of a
CAN network
The XCP messages are not described in the communication matrix! If measured values are
sent from the Slave via dynamic DAQ lists, e.g. with the help of XCP, the messages are
assembled according to the signals selected by the user. If the signal selection changes, the
message contents change as well. Nonetheless, there is a relationship between the commu
nication matrix and XCP: CAN identifiers are needed to transmit the XCP messages over
CAN. To minimize the number of CAN identifiers used, the XCP communication is limited to
the use of just two CAN identifiers that are not being used in the DBC for “normal” commu
nication. One identifier is needed to send information from the Master to the Slave; the
other is used by the Slave for the response to the Master.
The excerpt from the CANape Trace window shows the CAN identifiers that are used under
the “ID” column. In this example, just two different identifiers are used: 554 as the ID for the
message from Master to Slave (direction Tx) and 555 for sending messages from the Slave
to the Master (direction Rx).
1.4 XCP Transport Layers
51
Figure 38: Example of XCP-on-CAN communication
In this example, the entire XCP communication is handled by the two CAN identifiers 554
and 555. These two IDs may not be allocated for other purposes in this network.
The CAN bus transmits a maximum of eight useful bytes per message. In the case of XCP,
however, we need information on the command used or the sent response. This is provided
in the first byte of the CAN useful data. This means that seven bytes are available per CAN
message for transporting useful data.
XCP on CAN Message (Frame)
XCP Packet
XCP Tail
XCP Header
empty for CAN PID FILL DAQ TIMESTAMP
DATA
FILL
Control Field
Control Field
empty for CAN
for CAN
Figure 39: Representation of an XCP-on-CAN message
In CANape, you will find an XCPonCAN demo with the virtual ECU XCPsim. You can learn
about more details of the standard in ASAM XCP on CAN Part 3 Transport Layer
Specification.
52
1 Fundamentals of the XCP Protocol
1.4.2 CAN FD
CAN FD (CAN with flexible data rate) is an extension of the CAN protocol developed by
Robert Bosch GmbH. Its primary difference to CAN involves extending the useful data from
8 to 64 bytes. CAN FD also offers the option of sending the useful data at a higher data
rate. After the arbitration phase, the data bytes are sent at a higher transmission rate than
during the arbitration phase. This covers the need for greater bandwidth in automotive net
works while preserving valuable experience gained from CAN development.
The XCPonCANFD specification was defined in the XCPonCAN description of the XCP
standard, Version 1.2 (June 2013).
F
r1
K
O
r0
S
IDE
EDL
BRS
ESI
DLC
Data
CRC
elim.
AC
elim.
EOF
IFS
tifier
D
Iden
CK
CRC D
A
1
11
1
1
1
1
1
1
4
0…512
17/21
1
1
1
7
3
Arbitration phase
Data phase
Arbitration phase
(standard bit rate)
(optional high bit rate)
(standard bit rate)
EDL = Extended Data Length:
ESI = Error State Indicator:
CAN (dominant (0) = CAN frame
Dominant (0) = CAN FD node is error active
Recessive (1) = CAN FD frame
Recessive (1) = CAN FD node is error passive
BRS = Bit Rate Switch:
CAN FD data phase starts immediately at sampling point of BRS:
Dominant (0) = No change of bit rate for data phase
Recessive (1) = Change to higher bit rate for data phase
Figure 40: Illustration of a CAN FD frame
Despite the largely similar modes of operation, this protocol requires extensions and modifi
cations to the hardware and software. Among other things, CAN FD introduces three new
bits to the control field:
> Extended Data Length (EDL)
> Bit Rate Switch (BRS)
> Error State Indicator (ESI)
1.4 XCP Transport Layers
53
A recessive EDL bit (high level) distinguishes frames in extended CANFD format from those
in standard CAN format, because they are identified by a dominant EDL bit (low level). Sim
ilarly, a recessive BRS bit causes the transmission of the data field to be switched to the
higher bit rate. The ESI bit identifies the error state of a CAN FD node. Another four bits
make up what is known as the Data Length Code (DLC), which represents the extended
useful data length as a possible value of 12, 16, 20, 24, 32, 48 and 64 bytes.
The use of XCP on CAN FD assumes that a second transmission rate has been defined for
the useful data in the A2L file. This is fully transparent to the user, who gets a complete A2L
parameterization. A measurement configuration in the XCP Master considers the maximum
packet length, and the user does not need to make any other settings.
CAN FD is supported in CANape, Version 12.0 and higher. Every CAN hardware product from
Vector which begins with “VN” supports the CAN FD transport protocol.
54
1 Fundamentals of the XCP Protocol
1.4.3 FlexRay
A basic idea in the development of FlexRay was to implement a redundant system with
deterministic time behavior. The connection redundancy was achieved by using two chan
nels: channel A and channel B. If multiple FlexRay nodes (= ECUs) are redundantly intercon
nected and one branch fails, the nodes can switch over to the other channel to make use of
the connection redundancy.
Node K
Node L
Node M
Node N
Node O
CH A
CH B
Figure 41: Nodes K and L are redundantly interconnected
Deterministic behavior is achieved by transmitting data within defined time slots. Also
defined here is which node sends which content in which time slot. These time slots are com
bined to form one cycle. The cycles repeat here, as long as the bus is active. The assembly of
the time slots and their transport contents (who sends what at which time) is known as
scheduling.
Node K
Node L
Node M
Slot
Direction Frame
Slot
Direction Frame
Slot
Direction Frame
1
Tx
a
1
Tx
a
1
Tx
a
3
Rx
x
3
Rx
b
3
Rx
x
Frame: a
Frame: b
Frame: x
Frame: a
Frame: b
Frame: x
Slot 1
Slot 2
Slot 3
Slot 1
Slot 2
...
Real-time
t1
t2
t3
t4
t5
t6
Communication Cycle
Next Communication Cycle
Figure 42: Communication by slot definition
1.4 XCP Transport Layers
55
In the first communication cycle, node K sends frame a in slot 1. The scheduling is also stored
in the software of nodes L and M. Therefore, the contents of frame a are passed to the next
higher communication levels.
Scheduling is consolidated in a description file. This is not a DBC file, as in the case of CAN,
rather it is a FIBEX file. FIBEX stands for “Field Bus Exchange Format” and could also be
used for other bus systems. However, its current use is practically restricted to the descrip
tion of the FlexRay bus. FIBEX is an XML format and the XCPonFlexRay specification
relates to FIBEX Version 1.1.5 and FlexRay specification Version 2.1.
Cycles
Slot
ECU
Channel
0
1
2
3
4
5
6
...
63
A
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
1
Node K
ent
B
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
b [rep: 1]
egm
A
c [rep: 4]
x [rep: 2]
y [rep: 4]
x [rep: 2]
c [rep: 4]
x [rep: 2]
y [rep: 4]
x [rep: 2]
2
Node M
B
tatic S
A
a [rep: 1]
a [rep: 1]
a [rep: 1]
a [rep: 1]
a [rep: 1]
a [rep: 1]
a [rep: 1]
a [rep: 1]
S
3
Node L
B
d [rep: 1]
d [rep: 1]
d [rep: 1]
d [rep: 1]
d [rep: 1]
d [rep: 1]
d [rep: 1]
d [rep: 1]
Node L
A
n [rep: 1]
n [rep: 1]
n [rep: 1]
n [rep: 1]
n [rep: 1]
n [rep: 1]
n [rep: 1]
n [rep: 1]
4
Node O
B
m [rep: 1]
m [rep: 1]
m [rep: 1]
m [rep: 1]
m [rep: 1]
m [rep: 1]
m [rep: 1]
m [rep: 1]
Node N
A
r [rep: 1]
r [rep: 1]
r [rep: 1]
r [rep: 1]
r [rep: 1]
r [rep: 1]
r [rep: 1]
r [rep: 1]
ent
5
B
egm
A
6
ic S
Node K
B
o [rep: 1]
o [rep: 1]
o [rep: 1]
o [rep: 1]
o [rep: 1]
o [rep: 1]
o [rep: 1]
o [rep: 1]
Node M
A
t [rep: 2]
p [rep: 4]
t [rep: 2]
t [rep: 2]
p [rep: 4]
t [rep: 2]
ynam
D
B
Node L
A
u [rep: 4]
u [rep: 4]
7
Node L
B
v [rep: 8]
A
Node O
B
w [rep: 4]
w [rep: 4]
Figure 43: Representation of a FlexRay communication matrix
Another format for describing bus communication has been defined as a result of the devel
opment of AUTOSAR solutions: the AUTOSAR Description File, which is available in XML for
mat. The definition of XCPonFlexRay was taken into account in the AUTOSAR 4.0 specifi
cation. However, at the time of publication of this book this specification has not yet been
officially approved and therefore it will not be discussed further.
Due to other properties of the FlexRay bus, it is not sufficient to just give the slot number as
a reference to the contents. One reason is that multiplexing is supported: whenever a cycle
is repeated, the transmitted contents are not necessarily the same. Multiplexing might spec
ify that a certain piece of information is only sent in the slot in every second pass.
56
1 Fundamentals of the XCP Protocol
Instead of indicating the pure slot number, “FlexRay Data Link Layer Protocol Data Unit
Identifiers” (FLX_LPDU_ID) are used, which can be understood as a type of generalized Slot
ID. Four pieces of information are needed to describe such an LPDU:
> FlexRay Slot Identifier (FLX_SLOT_ID)
> Cycle Counter Offset (OFFSET)
> Cycle Counter Repetition (CYCLE_REPETITION)
> FlexRay Channel (FLX_CHANNEL)
LPDU_ID
...
Channel A
... ...
Channel B
ycle ID
C . . . . . . . . . .
. . . ...
.
. . . . .
. .. .. .. .. .. .. .. .. ..
.. .. .. .. ..
.. . . . . . . . . . . . . . . . . .
. .. .. .. .. .. .. .. .. ..
.
...
. .. .. .. ..
... ...
... ...
...
Figure 44:
Slot ID
Representation of the
FlexRay LPDUs
Scheduling also has effects on the use of XCP on FlexRay, because it defines what is sent
precisely. This cannot be readily defined in XCP; not until the measurement runtime does the
user define which measured values are sent by assembling signals. This means that it is only
possible to choose which aspect of XCP communication can be used in which LPDU: CTO or
DTO from Master to Slave or from Slave to Master.
The following example illustrates this process: the XCP Master may send a command (CMD)
in slot n and Slave A gives the response (RES) in slot n + 2. XCPonFlexRay messages are
always defined using LPDUs.
The A2L description file is needed for access to internal ECU parameters; the objects with
their addresses in the ECU are defined in this file. In addition, the FIBEX file is necessary, so
that the XCP Master knows which LPDUs it may send and to which LPDUs the XCP Slaves
send their responses. Communication between XCP Master and XCP Slave(s) can only func
tion through combination of the two files, i.e. by having an A2L file reference a FIBEX file.
1.4 XCP Transport Layers
57
Excerpt of an A2L with XCPonFlexRay parameter setting:
…
/begin XCP_ON_FLX
…
„XCPsim.xml“
„Cluster_1“
…
In this example, “XCPsim.xml” is the reference from the A2L file to the FIBEX file.
XCP-dedicated LPDU_IDs
...
Channel A
... ...
Channel B
ycle ID
C . . . . . . . . . .
. . . ...
.
. . . . .
. .. .. .. .. .. .. .. .. ..
.. .. .. .. ..
.. . . . . . . . . . . . . . . . . .
. .. .. .. .. .. .. .. .. ..
.
...
. .. .. .. ..
... ...
... ...
Figure 45:
...
Allocation of XCP
Slot ID
communication
to LPDUs
You can read more details about XCP on FlexRay in CANape’s Online Help. Supplied with
CANape is the FIBEX Viewer, which lets users conveniently view the scheduling. It is easy to
allocate the XCP messages to the LPDUs by making driver settings for the XCPonFlexRay
device in CANape.
The protocol is explained in detail in ASAM XCP on FlexRay Part 3 Transport Layer Specifi
cation. You will find an XCPonFlexRay demo in CANape with the virtual ECU XCPsim. The
demo requires real Vector FlexRay hardware.
1.4.4 Ethernet
XCP on Ethernet can be used with either TCP/IP or UDP/IP. TCP is a protected transport
protocol on Ethernet, in which the handshake method is used to detect any loss of a packet.
In case of packet loss, TCP organizes a repetition of the packet. UDP does not offer this pro
tection mechanism. If a packet is lost, UDP does not offer any mechanisms for repeated
sending of the lost packet on the protocol level.
Not only can XCP on Ethernet be used with real ECUs, it can also be used for measurement
and calibration of virtual ECUs. Here, a virtual ECU is understood as the use of code that
would other wise run in the ECU as an executable program (e.g. DLL) on the PC. Entirely dif
ferent resources are available here compared to an ECU (CPU, memory, etc.).
58
1 Fundamentals of the XCP Protocol
But first the actual protocol will be discussed. IP packets always contain the addresses of
the sender and receiver. The simplest way to visualize an IP packet is as a type of letter that
contains the addresses of the recipient and the sender. The addresses of individual nodes
must always be unique. A unique address comprises the IP address and port number.
XCP on Ethernet (TCP/IP and UDP/IP) Message (Frame)
XCP Header
XCP Packet
XCP Tail
empty for Ethernet
(TCP/IP and UDP/IP)
LEN
CTR
PID FILL DAQ
TIMESTAMP
DATA
Control Field
Length (LEN)
Control Field
for Ethernet
empty for Ethernet
(TCP/ IP and UDP/IP)
(TCP&IP and UDP&IP)
Figure 46: XCP packet with TCP/IP or UDP/IP
The header consists of a Control Field with two words in Intel format (= four bytes). These
words contain the length (LEN) and a counter (CTR). LEN indicates the number of bytes in
the XCP packet. The CTR is used to detect the packet loss. UDP/IP is not a protected proto
col. If a packet is lost, this is not recognized by the protocol layer. Packet loss is monitored by
counter information. When the Master sends its first message to the Slave, it generates a
counter number that is incremented with each additional transmission of a frame. The Slave
responds with the same pattern: It increments its own counter with each frame that it
sends. The counters of the Slave and the Master operate independently of one another.
UDP/IP is well suited for sending measured values. If a packet is lost, then the measured
values it contains are lost, resulting in a measurement gap. If this occurs infrequently, the
loss might just be ignored. But if the measured data is to be used as the basis for fast con
trol, it might be advisable to use TCP/IP.
An Ethernet packet can transport multiple XCP packets, but an XCP packet may never
exceed the limits of a UDP/IP packet. In the case of XCP on Ethernet, there is no “Tail”, i.e.
an empty control field.
1.4 XCP Transport Layers
59
Detection of XCP-on-Ethernet Slaves
With version 1.3 of the XCP standard, an expansion for XCP Slave detection was defined
specifically for XCP on Ethernet.
The Master can detect the XCP Slaves using the GET_SLAVE_ID command. Here, the Master
broadcasts a multicast message (IPv4) with the IP address 239.255.0.0 on port 5556.
Regardless of whether or not an XCP Slave already has a connection to a Master, the Slave
must process the request and return a response.
The response of the Slave contains, among other things:
> The IP address (IPv4)
> The port number
> TCP, UDP or both
> Information on the status of whether or not there is already a connection to an XCP
Master
You will find more detailed information on the protocol in ASAM XCP on Ethernet Part 3
Transport Layer Specification. In CANape, you will also find an XCP on Ethernet demo with
the virtual ECU XCPsim or with virtual ECUs in the form of DLLs, which have been imple
mented by Simulink models and the Simulink Coder.
1.4.5 SxI
SxI is a collective term for SPI or SCI. Since they are not buses, but instead are controller
interfaces which are only suited for pointtopoint connections, there is no addressing in this
type of transmission. The communication between any two nodes runs either synchronously
or asynchronously.
XCP on Sxl Message (Frame)
XCP Header
XCP Packet
XCP Tail
LEN
CTR
PID FILL DAQ
TIMESTAMP
DATA
FILL
CS
Control Field
Length (LEN)
Control Field
for SxI
for SxI
Checksum (CS)
Figure 47: XCP-on-SxI packet
The XCP header consists of a control field with two pieces of information: the length LEN
and the counter. The length of these parameters may be in bytes or words (Intel format).
LEN indicates the number of bytes of the XCP packet. The CTR is used to detect the loss of
a packet. This is monitored in the same way as for XCP on Ethernet: with counter informa
60
1 Fundamentals of the XCP Protocol
tion. Under certain circumstances it may be necessary to add fill bytes to the packet, e.g. if
SPI is used in WORD or DWORD mode or to avoid the message being shorter than the
minimal packet length. These fill bytes are appended in the control field.
You will find more detailed information on the protocol in ASAM XCP on SxI Part 3 Transport
Layer Specification.
1.4.6 USB
Currently, XCP on USB has no practical significance. Therefore, no further mention will be
made of this topic; rather we refer you to ASAM documents that describe the standard:
ASAM XCP on USB Part 3 Transport Layer Specification.
1.4.7 LIN
At this time, ASAM has not yet defined an XCPonLIN standard. However, a solution exists
from Vector (XCPonLIN driver and CANape as XCPonLIN Master), which violates neither
the LIN nor the XCP specification and is already being used on some customer projects. For
more detailed information, please contact Vector.
1.5 XCP Services
61
1.5 XCP Services
This chapter contains a listing and explanation of other services that can be realized over
XCP. They are all based on the already described mechanisms of communication with the
help of CTOs and DTOs. Some XCP services have already been explained, e.g. synchronous
data acquisition/stimulation and read/write access to device memory.
The XCP specification does indeed uniquely define the different services; at the same time it
indicates whether the service always needs to be implemented or whether it is optional. For
example, an XCP Slave must support “Connect” for the Master to set up a connection. On
the other hand, flashing over XCP is not absolutely necessary and the XCP Slave does not
need to support it. This simply depends on the requirements of the project and the software.
All of the services described in this chapter are optional.
1.5.1 Memory Page Switching
As already explained in the description of calibration concepts, parameters are normally
located in flash memory and are copied to RAM as necessary. Some calibration concepts
offer the option of switching memory segment pages from RAM and Flash. XCP describes a
somewhat more general, generic approach, in which a memory segment may contain multi
ple switchable pages. Normally, this consists of a RAM page and a flash page. But multiple
RAM pages or the lack of a flash page are conceivable as well.
For a better understanding of the XCP commands for page switching, the concepts of sec
tor, segment and page will be explained once again at this point.
XCP access
Segment 1
t 1
Segment 1
Segment 1
2
Page 0
Page 1
Page 2
egmem
S
tor
ec
S
ECU access
Segment 0
t 0
Page 0
1
egmem
S
tor
ec
S
0
tor
ec
address
S
Figure 48:
Memory representation
62
1 Fundamentals of the XCP Protocol
From an XCP perspective, the memory of a Slave consists of a continuous memory that is
addressed with a 40bit width. The physical layout of the memory is based on sectors.
Know ledge of the flash sectors is absolutely necessary in flashing, because the flash mem
ory can only be erased a block at a time.
The logical structure is based on what are known as segments; they describe where calibra
tion data is located in memory. The start address and parameters of a segment do not have
to be aligned with the start addresses and parameters of the physical sectors. Each seg
ment can be subdivided into multiple pages. The pages of a segment describe the same
parameters at the same addresses. The values of these parameters and read/write rights
can be controlled individually for each page.
The allocation of an algorithm to a page within a segment must always be unique. Only one
page may be active in a segment at any given time. This page is known as the “active page
for the ECU in this segment.” The particular page that the ECU and the XCP driver actively
access can be individually switched. No interdependency exists between these settings. Sim
ilar to the naming convention for the ECU, the active page for XCP access is referred to as
the “active page for XCP access in this segment“.
In turn, this applies to each individual segment. Segments must be listed in the A2L file and
each segment gets a number that is used to reference the segment. Within an XCP Slave,
the SEGMENT_NUMBER must always begin at 0 and it is then incremented in consecutive
numbers. Each segment has at least one page. The pages are also referenced by numbers.
The first page is PAGE 0. One byte is available for the number, so that a maximum of 255
pages can be defined per segment.
The Slave must initialize all pages for all segments. The Master uses the command
GET_CAL_PAGE to ask the Slave which page is currently active for the ECU and which page
for XCP access. It can certainly be the case that mutual blocking may be necessary for the
accesses. For example, the XCP Slave may not access a page, if this page is currently active
for the ECU. As mentioned, there may be a dependency – but not necessarily. It is a question
of how the Slave has been implemented.
If the Slave supports the optional commands GET_CAL_PAGE and SET_CAL_PAGE, then it
also supports what is known as page switching. These two commands let the Master poll
which pages are currently being used and if necessary it can switch pages for the ECU and
XCP access. The XCP Master has full control over switching of pages. The XCP Slave cannot
initiate switching by itself. But naturally the Master must respect any restrictions of the
Slave implementation.
What is the benefit of switching?
First, switching permits very quick changing of entire parameter sets – essentially a before
andafter comparison. Second, the plant remains in a stable state, while the calibrator per
forms extensive parameter changes on another page in the ECU. This prevents the plant
from going into a critical or unstable state, e.g. due to incomplete datasets during para
meter setting.
1.5 XCP Services
63
1.5.2 Saving Memory Pages – Data Page Freezing
When a calibrator calibrates parameters on a page, there is the conceptual ability in XCP to
save the data directly in the ECU. This involves saving the data of a RAM page to a page in
nonvolatile memory. If the nonvolatile memory is flash, it must be taken into account that
the segment start address and the segment size might not necessarily agree with the flash
sectors, which represents a problem in erasing and rewriting the flash memory (see ASAM
XCP Part 2 Protocol Layer Specification).
1.5.3 Flash Programming
Flashing means writing data in an area of flash memory. This requires precise knowledge of
how the memory is laid out. A flash memory is subdivided into multiple sectors (physical sec
tions), which are described by a start address and a length. To distinguish them from one
another, they each get a consecutive identification number. One byte is available for this
number, resulting in a maximum of 255 sectors.
SECTOR_NUMBER [0, 1, 2 … 255]
The information about the flash sectors is also part of the A2L data set.
Figure 49:
Representation
of driver settings
for the flash area
64
1 Fundamentals of the XCP Protocol
Flashing can be implemented using what are referred to as “flash kernels”. A flash kernel is
executable code that is sent to the Slave’s RAM area before the actual flashing; the kernel
then handles communication with the XCP Master. It might contain the algorithm that is
responsible for erasing the flash memory. For security and space reasons, very frequently
this code is not permanently stored in the ECU’s flash memory. Under some circumstances,
a converter might be used, e.g. if checksum or similar computations need to be performed.
Flashing with XCP roughly subdivides the overall flash process into three areas:
> Preparation (e.g. for version control and therefore to check whether the new contents can
even be flashed)
> Execution (the new contents are sent to the ECU)
> Postprocessing (e.g. checksum checking etc.)
In the XCP standard, the primary focus is directed to the actual execution of flashing. Any
one who compares this operation to flashing over diagnostic protocols will discover that the
processspecific elements, such as serial number handling with metadata, are supported in
a rather spartan fashion in XCP. Flashing in the development phase was clearly the main
focus in its definition and not the complex process steps that are necessary in endofline
flashing.
Therefore, what is important in the preparation phase is to determine whether the new con
tents are even relevant to the ECU. There are no special commands for version control.
Rather the practice has been to support those commands specific to the project.
The following XCP commands are available:
PROGRAM_START: Beginning of the flash procedure
This command indicates the beginning of the flash process. If the ECU is in a state that does
not permit flashing (e.g. vehicle speed > 0), the XCP Slave must acknowledge with an ERRor.
The actual flash process may not begin until the PROGRAM_START has been successfully
acknowledged by the Slave.
PROGRAM_CLEAR: Call the current flash memory erasing routine
Before flash memory can be overwritten with new contents, it must first be cleared. The call
of the erasing routine via this command must be implemented in the ECU or be made avail
able to the ECU with the help of the flash kernel.
PROGRAM_FORMAT: Select the data format for the flash data
The XCP Master uses this command to define the format (e.g. compressed or encrypted) in
which the data are transmitted to the Slave. If the command is not sent, the default setting
is noncompressed and nonencrypted transmission.
PROGRAM: Transfer the data to the XCP Slave
For the users who are very familiar with flashing via diagnostics: this command corresponds
to TRANSFERDATA in diagnostics. Using this command, data is transmitted to the XCP
Slave, which is then stored in flash memory.
1.5 XCP Services
65
PROGRAM_VERIFY: Request to check the new flash contents
The Master can request that the Slave perform an internal check to determine whether the
new contents are OK.
PROGRAM_RESET: Reset request to the Slave
Request by the Master to the Slave to execute a Reset. Afterwards, the connection to the
Slave is always terminated and a new CONNECT must be sent.
1.5.4 Automatic Detection of the Slave
The XCP protocol lets the Master poll the Slave about its protocolspecific properties. A
number of commands are available for this.
GET_COMM_MODE_INFO
The response to this command gives the Master information about the various communica
tion options of the Slave, e.g. whether it supports block transfer or interleaved mode or
which minimum time intervals the Master must maintain between requests in these modes.
GET_STATUS
The response to this request returns all current status information of the Slave. Which
resources (calibration, flashing, measurement, etc.) are supported? Are any types of mem
ory activities (DAQ list configuration, etc.) still running currently? Are DTOs (DAQ, STIM)
being exchanged right now?
GET_DAQ_PROCESSOR_INFO
The Master gets general information, which it needs to know about the Slave limitations:
number of predefined DAQ lists, available DAQ lists and events, etc.
GET_DAQ_RESOLUTION_INFO
Other information about the DAQ capabilities of the Slave is exchanged via this command:
maximum number of parameters for an ODT for DAQ and for STIM, granularity of the ODT
entries, number of bytes in timestamp transmission, etc.
GET_DAQ_EVENT_INFO
When this command is used, the call is made once per ECU event. Information is transmit
ted here on whether the event can be used for DAQ, STIM or DAQ/STIM, whether the event
occurs periodically and if so which cycle time it has, etc.
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1 Fundamentals of the XCP Protocol
1.5.5 Block Transfer Mode for Upload, Download and Flashing
In the “normal” communication mode, each command from the Master is acknowledged by
a response of the Slave. However, in some cases it may be desirable, for performance rea
sons, to use what is referred to as the block transfer mode.
Master
Slave
Request k
Part1
Part2
MIN_ST
Part3
MAX_BS
Response k
Request k+1
Time
Figure 50:
Representation of the block transfer mode
The use of such a method accelerates the procedure when transmitting large amounts of
data (UPLOAD, SHORT_UPLOAD, DOWNLOAD, SHORT_DOWNLOAD and PROGRAM). The
Master can find out whether the Slave supports this method with the request GET_COMM_
MODE_INFO. You will find more on this in ASAM XCP Part 2 Protocol Layer Specification.
1.5 XCP Services
67
1.5.6 Cold Start Measurement (during Power-On)
Even with the capabilities of XCP described to this point, it would be impossible to imple
ment an eventdriven measurement that can in practice be executed early in the ECU’s start
phase. The reason is that the measurement must be configured before the actual measure
ment takes place. If one attempts to do this, the ECU’s start phase has long been over by
the time the first measured values are transmitted. The approach that is used to overcome
this problem is based on a simple idea.
It involves separating the configuration and the measurement in time. After the configura
tion phase, the measurement is not started immediately; rather the ECU is shut down. After
a reboot, the XCP Slave accesses the existing configuration directly and immediately begins
to send the first messages. The difficulties associated with this are obvious: the configura
tion of the DAQ lists is stored in RAM, and therefore the information no longer exists after
a reboot.
To enable what is known as the RESUME mode to enable a Cold Start Measurement, a non
volatile memory is needed in the XCP Slave which preserves its data even when it is not
being supplied with power. EEPROMs are used in this method. In this context, it is irrelevant
whether it is a real EEPROM or one that is emulated by a flash memory.
You will find more details in ASAM XCP Part 1 Overview Specification in the chapter 1.4.2.2
“Advanced Features”.
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1 Fundamentals of the XCP Protocol
1.5.7 Security Mechanisms with XCP
An unauthorized user should be prevented as much as possible from being able to make a
connection to an ECU. The “seed & key” method is available for checking whether or not a
connection attempt is authorized. The three different access types can be protected by seed
& key: measurement / stimulation, calibration and flashing.
The “seed & key” method operates as follows: in the connect request by the Master, the
Slave sends a random number (= seed) to the Master. Now, the Master must use an algo
rithm to generate a response (= key). The key is sent to the Slave. The Slave also computes
the expected response and compares the key of the Master with its own result. If the two
results agree, both the Master and Slave have used the same algorithm. Then the Slave
accepts the connection to the Master. If there is no agreement, the Slave declines commu
nication with the Master.
Normally, the algorithm is available as a DLL in the Master. So, if a user has the “seed & key”
DLL and the A2L file, nothing stands in the way of accessing the ECU’s memory. When the
ECU is approaching a production launch, the XCP driver is often deactivated. A unique
sequence of individual diagnostic commands is usually used to restore XCP access to the
ECU. This makes the XCP driver largely available even in production vehicles, but it is nor
mally deactivated to protect against unauthorized manipulation of the ECU (see ASAM XCP
Part 2 Protocol Layer Specification).
Whether or not seed & key or deactivation of the XCP driver is used in a project is implemen
tationspecific and independent of the XCP specification.
2 ECU Description File A2L
71
2 ECU Description File A2L
72
2 ECU Description File A2L
One reason why an A2L file is needed has already been named: to allocate symbolic names
to addresses. For example, if a software developer has implemented a PID controller and
assigned the names P1, I1 and D1 in his application for the proportional, integral and differ
ential components, then the calibrator should be able to access these parameters with their
symbolic names. Let us take the following figure as an example:
Figure 51:
Parameters in a calibration window
The user can conveniently modify values using symbolic names. Another example is provided
by viewing signal variables that are measured from the ECU:
Figure 52: Signal response over time
In the legend, the user can read the logical names of the signals. The addresses at which the
parameters were located in the ECU are of secondary importance in the offline analysis of
values. Naturally, the correct address is needed to request the values in the ECU, but the
numeric value of the address itself is of no importance to the user. The user uses the logical
name for selection and visualization purposes. That is, the user selects the object by its
name and the XCP Master looks for the associated address and data type in the A2L.
2 ECU Description File A2L
73
Another attribute of a parameter might be the definition of a minimum or maximum value.
The value of the object would then have to lie within these limits. Imagine that you as the
software developer define a parameter that has a direct effect on a power output stage.
You must now prevent the user – whatever the user’s reasons might be – from configuring
the output stage that would result in catastrophic damage. You can accomplish this by
defining minimum and maximum values in the A2L to limit the permitted values.
Rules for conversion between physical and raw values are also defined in the A2L. You can
visualize a simple example of such a conversion rule in a sensor that has an 8bit value. The
numeric values output by the sensor lie between 0 and 255, but you wish to see the value as
a percentage value. Mapping of the sensor value [0 … 255] to [0 … 100 %] is performed with
a conversion rule, which in turn is stored in the A2L. If an object is measured, which exists as
a raw value in the ECU and is also transmitted as such, the measurement and calibration
tool uses the stored formula and visualizes the physical value.
Besides scalar parameters, characteristic curves and maps are frequently used. Some might
utilize a proximity sensor such as a Hall sensor, which determines distance as a function of
magnetic field strength and you may wish to use this distance value in your algorithm. The
magnetic field and distance value do not run linear to one another. This nonlinearity of
values would make formulation of the algorithm unnecessarily difficult. With the help of a
characteristic curve, you can first linearize the values before you input the values into your
algorithm as input variables.
Another application area for characteristic maps is their use as substitutes for complex
computations. For example, if there is a relationship y = f(x) and the function f is associated
with a lot of computing effort, it is often simpler to simply compute the values over the
potential range of x in advance and store the results in the form of a table (= characteristic
curve). If the value x is now in the ECU, the value y does not need to be computed at the con
troller’s runtime, rather the map returns the result y to the input variable x. It may be neces
sary to interpolate between two values, but that would be the extent of the calculations.
How is this characteristic curve stored in memory? Are all x values input first and then all y
values? Or does storage follow the pattern: x1, y1; x2, y2; x3, y3 …? Since various options are
available, the type of memory storage is defined in a storage scheme in the A2L.
The convenience for the user comes from the ability to work with symbolic names for param
eters, the direct look at the physical values and access to complex elements such as charac
teristic maps, without having to concern oneself with complex storage schemes.
Another advantage is offered by the communication parameters. They are also defined in
the A2L. In the communication between the measurement and calibration tool and the ECU,
the parameter set from the A2L is used. The A2L contains everything that the measurement
and calibration tool needs to communicate with the ECU.
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2 ECU Description File A2L
2.1 Setting Up an A2L File for an XCP Slave
The A2L file is an ASCIIreadable file, which describes the following with the help of
keywords:
> Interfacespecific parameters between measurement and calibration tool and A2L file
(the description is located at the beginning of the A2L file and is located in what is referred
to as the AML tree),
> Communication to the ECU,
> Storage scheme for characteristic curves and maps (keyword RECORD_LAYOUT),
> Conversion rules for converting raw values to physical values (keyword COMPU_METHOD),
> Measurement parameters (keyword MEASUREMENT),
> Calibration parameters (keyword CHARACTERISTIC) and
> Events that are relevant for triggering a measurement keyword EVENT),
A summary of parameters and measurement parameters is made with the help of groups
(keyword GROUP).
Example of a measurement parameter with the name “Shifter_B3”:
/begin MEASUREMENT Shifter_B3 „Single bit signal (bit from a byte shifting)“
UBYTE HighLow 0 0 0 1
READ_WRITE
BIT_MASK 0x8
BYTE_ORDER MSB_LAST
ECU_ADDRESS 0x124C02
ECU_ADDRESS_EXTENSION 0x0
FORMAT „%.3“
/begin IF_DATA CANAPE_EXT
100
LINK_MAP „byteShift“ 0x124C02 0x0 0 0x0 1 0x87 0x0
DISPLAY 0 0 20
/end IF_DATA
/end MEASUREMENT
Example of a parameter map with the name KF1:
/begin CHARACTERISTIC KF1 „8*8 BYTE no axis“
MAP 0xE0338 __UBYTE_Z 0 Factor100 0 2.55
ECU_ADDRESS_EXTENSION 0x0
EXTENDED_LIMITS 0 2.55
BYTE_ORDER MSB_LAST
BIT_MASK 0xFF
/begin AXIS_DESCR
FIX_AXIS NO_INPUT_QUANTITY BitSlice.CONVERSION 8 0 7
EXTENDED_LIMITS 0 7
2.1 Setting Up an A2L File for an XCP Slave
75
READ_ONLY
BYTE_ORDER MSB_LAST
FORMAT „%.0“
FIX_AXIS_PAR_DIST 0 1 8
/end AXIS_DESCR
/begin AXIS_DESCR
FIX_AXIS NO_INPUT_QUANTITY BitSlice.CONVERSION 8 0 7
EXTENDED_LIMITS 0 7
READ_ONLY
BYTE_ORDER MSB_LAST
FORMAT „%.0“
FIX_AXIS_PAR_DIST 0 1 8
/end AXIS_DESCR
/begin IF_DATA CANAPE_EXT
100
LINK_MAP „map3_8_8_uc“ 0xE0338 0x0 0 0x0 1 0x87 0x0
DISPLAY 0 0 255
/end IF_DATA
FORMAT „%.3“
/end CHARACTERISTIC
The ASCII text is not easy to understand. You will find a description of its structure in ASAM
XCP Part 2 Protocol Layer Specification in chapter 2.
The sections below describe how to create an A2L. Let us focus on the actual contents of an
A2L and their meanings and leave the details of the A2L description language to an editor.
The A2L Editor that is supplied with CANape is used here.
2.2 Manually Creating an A2L File
The A2L mainly describes the contents of the memory of the XCP Slave. The contents depend
on the application in the Slave, which was developed as C code. After the compiler/linker run
of the application code, important elements of an A2L file already exist in the linkermap file:
the names of the objects, their data types and memory addresses. Still lacking are the
parameters for communication between XCP Master and Slave. Other information is usually
needed such as minimum and maximum values of parameters, conversion rules, storage
schemes for characteristic maps etc.
Let us begin by creating an empty A2L and the communication parameters: If you wish to
create an A2L that describes an ECU with an XCPonCAN interface, for example, you cre
ate a new device in CANape and select XCP on CAN as the interface. Then you can supple
ment this with other communicationspecific information (e.g. CAN identifiers). After saving
the file, you have an A2L that contains the entire communication content of the A2L. Still
lacking are the definitions of the actual measurement and calibration parameters.
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2 ECU Description File A2L
In the A2L Editor, the linkermap file is associated to the A2L. In a selection dialog, the user
can now select those parameters from the map file which it needs in the A2L: scalar
measurement and calibration parameters, characteristic curves and maps. The user can
gradually add the desired parameters to the A2L step by step and group them. Other object
specific information is also added using the editor.
What should be done when you modify your code, recompile it and link it? It is highly proba
ble that the addresses of objects will change. Essentially, it is not necessary to generate a
new A2L. If you wish to have objects just added to the code also be available in the A2L, you
must of course add them to the A2L. Address updating is always necessary in the A2L. This
is done with the editor; it searches for the relevant entry in the linkermap file based on the
name of the A2L object, reads out the address and updates it in the A2L.
If your application changes very dynamically – objects are renamed, data types are adapted,
parameters are deleted and others added – then the manual work method is impractical. To
generate an A2L from a C code, other tools are available for automatic processing.
On the Vector homepage you will find information on the “ASAP2 ToolSet“ with which you
can automate the generation of A2Ls from the source code in a batch process.
2.3 A2L Contents versus ECU Implementation
When an XCP Master tool reads in an A2L that does not fully match the ECU, misunder
standings in the communication might occur. For example, another value related to time
stamp resolution might be in the A2L file that differs from the value implemented in the
ECU. If this is the case, the problem must be detected and solved. The user gets support
from the Master, who can poll the Slave via the protocol to determine what was really imple
mented in the Slave.
XCP offers a number of functions that were developed for automatic detection of the Slave.
Of course, this assumes that automatic detection is implemented in the Slave. If the Master
polls the Slave and the Slave’s responses do not agree with the parameter set of the A2L
description file, the Master must decide which settings to use. In CANape, the information
that is read out by the Slave is given a higher priority than the information from the A2L.
2.3 A2L Contents versus ECU Implementation
77
Here is an overview of possible commands that are used to find out something about the
XCP implementation in the Slave:
GET_DAQ_PROCESSOR_INFO
Returns general information on the DAQ lists: MAX_DAQ, MAX_EVENT_CHANNEL,
MIN_DAQ
GET_DAQ_RESOLUTION_INFO
Maximum parameter of an ODT entry for DAQ/STIM, time interval information
GET_DAQ_EVENT_INFO (Event_channel_number)
Returns information for a specific time interval: Name and resolution of the time interval,
number of DAQ lists that may be assigned to this time interval …
GET_DAQ_LIST_INFO (DAQ_List_Number)
Returns information on the selected DAQ list: MAX_ODT, MAX_ODT_ENTRIES exist as pre
defined DAQ lists …
3 Calibration Concepts
79
3 Calibration Concepts
80
3 Calibration Concepts
ECU parameters are constant parameters that are adapted and optimized during the
development of the ECU or an ECU variant. This is an iterative process, in which the optimal
value of a parameter is found by repeated measurements and changes.
The calibration concept answers the question of how parameters in the ECU can be changed
during an ECU’s development and calibration phases. There is not one calibration concept
that exists, rather several. Which concept is utilized usually depends very much on the capa
bilities and resources of the microcontroller that is used.
Normally, parameters are stored in the production ECU’s flash memory. The underlying pro
gram variables are defined as constants in the software. To make parameters modifiable at
runtime during an ECU’s development, additional RAM memory is needed.
A calibration concept is concerned with such questions as these: How do the parameters ini
tially find their way from flash to RAM? How is the microcontroller’s access to RAM rerouted?
What does the solution look like when there are more parameters than can be simultane
ously stored in RAM? How are the parameters copied back into flash? Are changes to the
parameters persistent, i.e. are they preserved when the ECU is turned off?
A distinction is made between transparent and nontransparent calibration concepts. Trans
parent means that the calibration tool does not need to be concerned with the above
questions, because all necessary mechanisms are implemented in the ECU.
Several methods are briefly introduced in the following.
3.1 Parameters in Flash
The software developer defines in the source code whether a parameter is a variable or a
constant, i.e. whether a parameter is stored in flash or in RAM memory.
C code example:
const float factor = 0.5;
The “factor” parameter represents a constant with the value 0.5. During compiling and link
ing of the code, memory space is provided in flash for the “factor” object. The object is allo
cated an address that lies in the data area of the flash memory. The value 0.5 is found at
the relevant address in the hex file and the address appears in the linkermap file.
The simplest conceivable calibration concept involves modifying the value in C code, gener
ating a new hex file and flashing. However, this method is very laborious, because every
value change must be made in code, resulting in the need for a compiler/linker run with sub
sequent flashing. An alternative approach would be to only modify the value in the hex file
and then reflash this file. Every calibration tool is capable of doing this. It is referred to as
“offline calibration” of the hex file, which is a very commonly used method.
3.1 Parameters in Flash
81
Under some circumstances, with certain compilers it may be necessary to explicitly ensure
that parameters are always also stored in flash memory and not integrated in the code, for
example and therefore do not appear at all in the linkermap file. Usually, one does not want
to leave to chance where a constant is created in flash memory. The necessary means for
accomplishing this are almost always compilerspecific pragma instructions. To prevent the
compiler from embedding them in the code, it is generally sufficient to use the “volatile”
attribute for constant parameters. A typical definition of a flash constant appears as in the
following example:
C code example:
#pragma section “FLASH_Parameter”
volatile const float factor = 0.5;
It is normally not possible to calibrate parameters in flash online. Indeed, most microcon
trollers are able to program their flash themselves, which is necessary for the purposes of
reprogramming in the field. Nonetheless, flash memory always has the property of being
organized into larger blocks (sectors), which can only be erased as a whole. It is practically
impossible to flash just individual parameters, because the ECU normally does not have the
resources to buffer the rest of the sector and reprogram it. In addition, this process would
take too much time.
Some ECUs have the ability to store data in what is known as an EEPROM memory. In con
trast to flash memories, EEPROM memories can erase and program each memory cell indi
vidually. The amount of available EEPROM memory is always considerably less than the
available flash memory and it is usually limited to just a few kilobytes. EEPROM memory is
often used to store programmable parameters in the service shop or to implement a persis
tence mechanism in the ECU, e.g. for the odometer. Online calibration would be conceivable
here, but it is seldom used, because access to EEPROM cells is relatively slow and during the
booting process EEPROM parameters are usually copied over to RAM memory, where it is
possible to access them directly. ECUs which have no EEPROM memory often implement
what is known as an EEPROM emulation. In this method, multiple small flash sectors are
used in alternation to record parameter changes, so that the last valid value can always be
determined. Online calibration would also be conceivable with this method.
In both cases, the relevant memory accesses would then be intercepted in the software
components of the XCP driver and implemented with the software routines of the EEPROM
or the EEPROM emulation. The Vector XCP Professional driver offers the software hooks
needed for this.
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3 Calibration Concepts
3.2 Parameters in RAM
The most frequently used approach to modifying parameters at runtime (“online calibra
tion”) is to create the parameters in the available RAM memory.
C code example:
#pragma section “RAM_Parameter”
volatile float factor = 0.5;
This defines the parameter “factor” as a RAM variable with the initial value 0.5. During com
piling and linking of the code, memory space is reserved for the object “factor” in RAM and
the associated RAM address appears in the linkermap file. The initial value 0.5 is stored in
flash memory and at the relevant location in the hex file. The addresses of the initial values
in flash memory are defined by parameterization of the linker, but they do not appear in the
linkermap file.
During booting of the ECU, all RAM variables are initialized once with their initial values
from flash memory. This is usually executed in the startup code of the compiler producer
and the application programmer does not need to be concerned with it. The application uses
the values of parameters located in RAM and they can be modified via normal XCP memory
accesses.
From the perspective of the ECU software, calibration parameters in RAM are always still
unchangeable, i.e. the application itself does not change them. Many compilers discover this
fact by code analysis and simply optimize the necessary RAM memory space away. Nor
mally, it is therefore also necessary to prevent the compiler from optimizing by using the
“volatile” attribute.
From the perspective of the calibration tool, the RAM area in which the parameters are
located is referred to as calibration RAM (memory that can be calibrated).
FLASH
RAM
Calibration RAM
Parameters
Figure 53:
Initial parameter setting in RAM
The calibration RAM does not need to consist of a fully contiguous RAM area. It may also be
distributed into multiple areas or even in any desired way. Nonetheless, it offers significant
advantages for organizing the parameters in just a few contiguous RAM areas and isolating
them from other RAM parameters such as changing state variables and intermediate
results. This is especially important if offline calibration of the calibration RAM with a hex
file should be enabled. At the user’s request, the calibration tool must be able to load the
3.2 Parameters in RAM
83
parameters that were modified offline into the ECU during the transition from offline cali
bration to online calibration.
This case occurs very frequently. For example, when calibrators reconnect with their ECU on
the next work day, they want to resume work at the point at which they stopped the evening
before. However, booting of the ECU causes the flashed contents to be copied to the RAM
as an initial dataset. To let users resume with work accomplished on the previous day, the
parameter set file saved the previous evening in the ECU’s RAM must be loaded. This load
ing process may be time optimized by limiting the number of necessary transmissions to a
minimum. It is advantageous here if the tool can quickly and reliably determine – by forming
a checksum over larger contiguous areas – whether there are differences. If there are no dif
ferences between the calibration RAM contents in the ECU and the file modified using the
tool, this area does not need to be transferred. If the memory area with the calibration
parameters is not clearly defined, or if it includes parameters that are modified by the ECU
software, a checksum calculation always shows a difference and the parameter values are
transmitted, either from the ECU to the XCP Master or in a reverse direction. Depending on
the transmission speed and amount of data, this transmission could take several minutes.
Another advantage of clearly defined memory segments is that the memory area for initial
values in flash memory can be used for offline calibration. The contents of the flash memory
are defined using flashable hex files. If the calibration tool knows the location of parameters
in the hex file, it can modify their values and implement new initial values in the ECU by
flashing the modified hex file.
The calibration tool not only needs to know the location of parameters in RAM, but also the
initial values in flash. A prerequisite is that the RAM memory segment must be initialized by
copying from an identically laid out memory segment in flash, as is the usual practice in
most compilers/linkers. If the addresses of parameters in RAM are in the A2L file, it is only
necessary to let the tool know the offset to the start address of the calibration RAM, which
it must add to get to the start address of the relevant flash area. This offset then applies to
each individual parameter in the A2L.
The calibration tool can then either generate flashable hex files for this area itself, or it can
place them directly on the original hex files of the linker to modify the initial values of para
meters in the hex file.
84
3 Calibration Concepts
3.3 Flash Overlay
Many microcontrollers offer options for overlaying memory areas in flash with internal or
external RAM. This process is referred to as flash emulation or flash overlay. A lot is possible,
from the use of a Memory Management Unit all the way to dedicated mechanisms that pre
cisely serve this purpose. In this case the parameters are created as parameters in flash just
as in calibration concept 1. This method offers enormous advantages compared to the
described calibration concept 2 “Parameters in RAM”:
> No distinction is made between flash and RAM addresses. The flash addresses are always
located in the A2L file, the hex file and linkermap file. This produces clear relationships,
the hex file is directly flashable and the A2L file matches it exactly.
> The overlay can be activated or deactivated as a whole, which enables lightningquick
swapping between values in flash and those in RAM. They are referred to as the RAM page
and the flash page of a memory segment. XCP supports control of memory page switch
ing with special commands.
> The memory pages might be switched separately, e.g. for XCP access and ECU access, i.e.
XCP could access a memory page while the ECU software works with the other page. This
permits such operations as downloading of the offline calibration data to RAM, while the
ECU is still working with the flash data; this avoids potential inconsistencies that could be
problematic on a running ECU.
> The overlay with RAM does not need to be complete and it can be adapted to the applica
tion case. It is possible to work with less RAM than with flash. More on this later.
A typical procedure for connecting the calibration tool to the ECU with the subsequent
download of values that were calibrated offline appears as follows:
Connects to the ECU
CONNECT
Connects XCP Master to RAM page
SET_CAL_PAGE XCP to RAM
Checksum calculation
CALC_CHECKSUM
When a difference has been detected in the checksum calculation over the RAM area, first
the user is normally asked how to proceed. Should the contents of ECU RAM be sent to the
Master, or should the contents of a file on the Master page be sent to the ECU’s RAM? If the
user decides to write the offline changes to the ECU, the subsequent process appears as
follows:
ECU should use the dataset of the flash page SET_CAL_PAGE ECU to FLASH
Copy file from Master to the RAM page
DOWNLOAD …
ECU should use the dataset of the RAM page SET_CAL_PAGE ECU to RAM
Afterwards, the memory page is always switched over to RAM, so that parameters can be
modified. But the user can also explicitly indicate which memory page should be active in the
ECU. For example, the behavior of the RAM parameter set can be compared to that of the
flash parameter set, or in an emergency it can be switched back to a proven parameter set
in flash at lightning speed.
3.4 Dynamic Flash Overlay Allocation
85
3.4 Dynamic Flash Overlay Allocation
The concepts for calibration RAM described so far are unproblematic if sufficient RAM is
available for all parameters. But what if the total number of parameters does not fit into
the available RAM area?
Here, it is advisable to overlay flash with RAM dynamically and do not overlay the affected
flash memory with RAM until the actual write access to a parameter. This procedure can
occur with a certain granularity and – depending on the implementation – it may be trans
parent to the calibration tool from the XCP perspective. If the XCP driver detects a write
access to flash in the ECU which would lead to a change, a part of calibration RAM is used
to copy over the relevant part of flash and activate the overlay mechanism for this part. This
involves allocating the RAM, i.e. in a fixed layout and it is identified as utilized. However, the
resources of the calibration RAM are limited. During the calibration process, RAM area that
has already been allocated is no longer released, so the available calibration RAM dwindles
with further requests. If the RAM resources are used up and a new allocation is required, the
user is informed of the exhausted RAM resources. The user is offered the option of flashing
or saving the changes made up to that point. This frees up the allocated RAM area again
and the user can once again calibrate. The variant in which the ECU autonomously flashes
the previously changed parameters is usually ruled out here for the reasons already cited in
calibration concept “Parameter in Flash”.
In some cases, the download of a parameter set created offline might not be executable due
to insufficient RAM resources. The only alternative is to flash it. The user can always cancel
the changes from the tool and this releases the allocated RAM blocks again.
In this concept, page switching between the RAM and flash pages is also possible without
any limitations. The parameters should be organized together in flash according to function,
so that the available RAM blocks can be used as efficiently as possible. The software devel
oper then specifies that the parameters, which belong together thematically, also lie in a
contiguous memory area. After copying to RAM, the parameters needed for tuning the par
ticular function are fully ready for use.
86
3 Calibration Concepts
3.5 RAM Pointer Based Calibration Concept per AUTOSAR
This concept does not require necessarily the use of an AUTOSAR operating system; it can
even be used in a different environment – e.g. without an operating system. The concept
exhibits a key similarity to the previous concept. The primary difference is that the substitu
tion of flash for RAM is not implemented by hardware mechanisms, but by software mech
anisms instead. The calibration parameters are always referenced by pointers from the ECU
software. Flash or RAM contents are accessed by changing this pointer. The flash parame
ters to be modified are copied to a defined block with available RAM. This method can be
implemented fully transparently from the XCP perspective, just as in the previous method.
As an alternative, the user of the calibration tool can explicitly select the parameters to be
modified by preselecting the desired parameters. The advantage of this is that resource uti
lization and loading is visible to the user and the user is not surprised by a lack of memory in
the midst of working.
3.5.1 Single Pointer Concept
The pointer table is located in RAM. When booting the ECU, all pointers indicate the para
meter values in flash. The location and parameters of the calibration RAM are indeed known,
but it does not yet contain any parameter values after booting. Initially, the application
works entirely from flash.
FLASH
Pointertable
RAM
Parameters
Figure 54:
Initial situation after booting
When the user selects a parameter from the A2L file for the first time after booting and
wishes to write access it, this triggers a copying operation within the ECU first. The XCP
Slave determines that the address to which the access should be made is located in the
flash area, and it copies the parameter value to the calibration RAM. A change is also made
in the pointer table to ensure that the application no longer gets the parameter value from
flash, but instead from the RAM area:
3.5 RAM Pointer Based Calibration Concept per AUTOSAR
87
FLASH
Pointertable
RAM
Parameters
Figure 55:
Pointer change and copying to RAM
The application continues to get the parameter value via the pointer table. But since the
pointer indicates the RAM address, the value is retrieved from there. As a result, the user can
change the parameter value via XCP and observe the effects of the change in the measure
ment. The disadvantage of this method is that an entry in a pointer table must be available
for each parameter and in turn the method is associated with substantial additional RAM
memory requirements for the pointer table.
The next figure illustrates the problem. Three parameters of a PID controller (P, I and D) are
contained in an ECU’s flash area. The RAM addresses and parameter values in RAM are also
already changed in the pointer table.
Parameter
Flash
Pointertable
RAM
Address
Content
Address
Address
Content
P
0x0000100A 0x11
0x000A100A
0x000A100A 0x44
I
0x000012BC 0x22
0x000A100B
0x000A100B 0x55
D
0x00007234 0x33
0x000A100C
0x000A100C 0x66
Figure 56: Pointer table for individual parameters
Calibration concepts are very important, because RAM resources are scarce. Large RAM
pointer tables would make a concept selfdefeating.
To avoid having to create a pointer for each individual parameter and having the method be
used as such, the parameters can be combined into structures. This requires just one pointer
per structure. When the user selects a parameter, not only is this parameter copied to RAM,
but so is the entire associated structure. The granularity of the structures is of key impor
tance here. With large structures only a few pointers are necessary. In turn, this means that
with the decision for a specific parameter, a rather large associated structure is copied to
the RAM area and this can cause the limits of calibration RAM space to be reached quickly.
88
3 Calibration Concepts
Example:
The calibration RAM should be 400 bytes in size. Four structures are defined in the software
with the following parameters:
Structure A: 250 bytes
Structure B: 180 bytes
Structure C: 120 bytes
Structure D: 100 bytes
When the user selects a parameter from structure A, the 250 bytes are copied from flash to
the calibration RAM, and the user has XCP access to all parameters located in structure A.
If the calibration task is limited to the parameters of this structure, the calibration RAM is
fully sufficient. However, if the user selects another parameter located in a different struc
ture, e.g. structure C, these 120 bytes must also be copied to the calibration RAM. Since the
calibration RAM can handle 400 bytes, the user can access all parameters of structures A
and C simultaneously.
If another selected parameter is not located in structure C, but rather in structure B, the 180
bytes of structure B would have to be copied to RAM in addition to the 250 bytes of struc
ture A. However, since the space in RAM is inadequate for this, the user indeed has access to
the parameters of structure A, but not to the data of structure B, because the ECU cannot
execute the copy command.
You can learn more about how this approach works in CANape. Start CANape with the
“AUTOSAR Single Pointered Demo” project. You will find more information on its use in
CANape on the “Introduction” page of the project.
You will find a source code example under the “Demos” category at the Vector Download
Center. A code example on how to use the calibration concept is contained in the “XCP Sample
Implementation” under <Installation DIR>\Samples\CAN\CAN MPC55xx\XCPDemo.
3.5.2 Double Pointer Concept
A disadvantage of the single pointer concept is that memory page switching is not easy to
implement. The calibration tool could simply describe the pointer table completely for page
swapping, but this is not feasible in a short period of time without resulting in temporary
inconsistencies and side effects. A tooltransparent implementation would double the mem
ory space requirement for the pointer table, because when switching the memory page into
flash, a copy of the previous pointer table would have to be created with RAM pointers.
For applications with large pointer tables, a transparent implementation or a fully consis
tent switching, there is the option of extending the method to a double pointer concept. To
explain how this is done, we return once again to the initial RAM setting.
3.5 RAM Pointer Based Calibration Concept per AUTOSAR
89
Figure 57 represents the pointer table. It lies in RAM. As already mentioned, this table must
be copied from flash into RAM. As a result, this table lies in flash memory. If another pointer
is now used (a table pointer), which points to either the pointer table in RAM or in flash, one
arrives at a double pointer solution.
FLASH
RAM
Pointertable
FLASH
Pointertable
RAM
Tablepointer
Figure 57:
Double pointer concept
The parameter values are initially accessed via the table pointer. If the table pointer indi
cates the pointer table in RAM, the application essentially accesses the actual parameters
via the contents of the RAM pointer table. The low access speed and the creation of more
program code are disadvantages of this solution.
3.6 Flash Pointer Based Calibration Concept
This method was patented several years ago by the company ZF Friedrichshafen under the
name “InCircuit2” and bears a strong resemblance to the pointerbased concept of AUTOSAR.
Here too, the application in the ECU accesses parameter data using a pointer table. How
ever, this pointer table is not located in RAM, but in flash instead. Changes to the pointer
table can therefore only be made by flash programming. A tooltransparent implementation
is not possible. The advantage lies in the RAM memory that is saved since it no longer con
tains the pointer table.
You can find out how this approach works in CANape. Start CANape with the “InCircuit2”
project. You will find more information on its use in CANape on the “Introduction” page of
the project.
4 Application Areas of XCP
91
4 Application Areas of XCP
92
4 Application Areas of XCP
When ECU calibrators think about the use of XCP, they are usually fixated on use of the pro
tocol in the ECU.
Simulink
Slave
Prototype or
ECU Hardware
Slave
Measurement/
XCP
Calibration
Master
Slave
PC
Hardware*
EXE/DLL
Slave
HIL/SIL Systems
Slave
Figure 58:
Application areas and
* Debug Interfaces, Memory Emulator ...
application cases
In a survey of development processes, one encounters many different solution approaches
for the development of electronics and software. HIL (Hardware in the Loop), SIL (Software
in the Loop) and Rapid Prototyping are keywords here and they describe different scenarios.
They always have a “plant” and a “controller” in common.
Manipulated Disturbance
Offset
Variable
Variable
Reference Variable
Controller
Plant
Controlled Variable
(Set Value)
(Actual Value)
Figure 59: Plants and controllers
In the context of automotive development, the controller is represented by the ECU and the
plant is the physical system to be controlled such as the transmission, engine, side mirrors,
etc.
The rough subdivision is made between different development approaches according to
whether the controller or the plant runs in real or simulated mode. Some combinations will
be described in greater detail.
4.1 MIL: Model in the Loop
93
4.1 Model in the Loop (MIL)
Simulink
Controller Model
Plant Model
Figure 60:
Model in the Loop
in Simulink
In this development environment, both the controller and the plant are simulated as a
model. In the example shown, both models run in Simulink as the runtime environment. The
capabilities of the Simulink runtime environment are available to you for analyzing the
behavior.
To realize the convenience of a measurement and calibration tool like CANape in an early
development phase, an XCP Slave can be integrated in the controller model. In an authoring
step, the Slave generates the A2L that matches the model and the user already has the full
range of convenient operating features with visualization of process flows in graphic win
dows, access to characteristic curves and maps and much more.
Simulink
Controller Model
Plant Model
CANape
Simulink
Figure 61:
XCP Server
CANape as measurement
A2L
and calibration tool
with Simulink models
Neither a code generation step nor instrumentation of the model is necessary for this. Time
stamps are also included with transmissions over XCP. CANape completely adapts to the
time behavior of the Simulink runtime environment here. Whether the model is running
faster or slower than in real time is of no consequence. For example, if the functional devel
oper uses the Simulink Debugger in the model to step through the model, CANape still takes
the time transmitted via XCP as the reference time.
94
4 Application Areas of XCP
4.2 Software in the Loop (SIL)
Simulink
Controller Model
Plant Model
Code Generation
Controller Model
Figure 62:
Windows DLL
Software in the Loop
with Simulink
environment
In this development step, code is generated from the model of the controller, which is then
used in a PCbased runtime environment. Naturally, the controller may also have been devel
oped without any sort of modelbased approach. The plant continues to be simulated. XCP
can be used to measure and calibrate the controller. If the controller originates from a
Simulink model, a code generation step (Simulink Coder with the target “CANape”) is used
to generate the C code for a DLL and the associated A2L. If the Controller development is
conducted based on manually written code, it is embedded in a C++ project that is delivered
with CANape.
After compiling and linking, the DLL is used in the CANape context. With the support of the
XCP connection, the algorithms in the DLL can be measured and calibrated exactly as if the
application were already integrated in an ECU.
Simulink
Controller Model
Plant Model
Code generation
Controller Model
CANape
Windows DLL
A2L
Figure 63:
CANape as SIL
development platform
4.3 HIL: Hardware in the Loop
95
4.3 Hardware in the Loop (HIL)
Many different kinds of HIL systems are available. They range from very simple, costeffec
tive systems all the way to very large and expensive expansion stages. The following figure
shows the rough concept:
Controller Model
HIL Platform
I/O
Plant Model
ECU
Figure 64:
HIL solution
The controller algorithm runs in a microcontroller platform (e.g. the ECU), while the plant
continues to be simulated. Depending on the parameters and the complexity of the plant
and the necessary I/O, requirements of the HIL platform and the associated costs can rise
steeply. Since the ECU runs in real time, the model of the plant must also be computed in
real time.
To now introduce XCP for optimization appears trivial, because another ECU is being added.
The whole system looks like this:
Controller Model
A2L
HIL Platform
I/O
CANape
Plant Model
Figure 65:
HIL with CANape
ECU
as measurement and
calibration tool
From CANape, the user has access to the algorithms in the ECU over XCP.
96
4 Application Areas of XCP
The Vector Tool CANoe is also used by many customers as a HIL system. With CANoe, a HIL
system might look like this:
CANoe RT User PC
Ethernet
CANoe RT Server
CAN
LIN
Plant Model
MOST
A2L
FlexRay
Digital I/O
Analog I/O
XCP
CANape
ECU
Figure 66:
CANoe as HIL system
The ability to access XCP data directly from CANoe for testing purposes results in the fol
lowing variant as well:
CANoe RT User PC
A2L
Ethernet
CANoe RT Server
CAN
LIN
Plant Model
XCP
MOST
FlexRay
Digital I/O
Analog I/O
Figure 67:
CANoe as HIL system
with XCP access
ECU
to the ECU
Here the model of the plant runs on the CANoe realtime server. At the same time, XCP
access to the ECU is also realized from CANoe. This gives a tool simultaneous access to the
plant and the controller.
4.3 HIL: Hardware in the Loop
97
To round out the picture, yet another HIL solution option should be mentioned. The plant
might also run as a DLL in CANape. This gives the user full access to the plant and to the
controller over XCP.
ECU
CANape
Plant Model
A2L
Windows DLL
XCP
Plant
A2L
XCP
ECU
Figure 68: CANape as HIL solution
4.4 Rapid Control Prototyping (RCP)
In this development phase, the control algorithm runs on realtime hardware instead of an
ECU. This situation often occurs when the necessary ECU hardware is not yet available.
Several platforms come in question as suitable hardware: from simple evaluation boards all
the way to special automotivelevel hardware solutions, depending on which additional
requirements need to be fulfilled. Here too, integration with XCP helps in setting up an OEM
independent tool chain.
Controller Model
CANape
EVA Board
A2L
XCP
I/O
Plant
Figure 69: Solution for Rapid Control Prototyping
The concepts “Rapid” and “Prototyping” describe the task very well. The aim is to develop a
functional prototype as quickly as possible, to use and test it in the runtime environment.
This just requires simple work steps throughout the entire process.
98
4 Application Areas of XCP
In the literature, the RCP approach is frequently subdivided into two areas: fullpassing and
bypassing.
As depicted in Figure 69, the entire controller runs on separate realtime hardware. This
method is known as fullpassing, because the entire controller runs on the controller hard
ware. It must have the necessary I/O to be able to interface with the plant. Very often, it is
only possible to fulfill technical requirements for the I/O with suitable power electronics.
It is not only the I/O that represents a challenge; often functional elements of the ECU soft
ware (e.g. network management) are needed to enable functionality in a more complex net
work. However, if a complete ECU is used for Rapid Control Prototyping instead of a general
controller platform, the complexity of the flash process, the size of the overall software, etc.
all work against the requirement for “rapid” development.
In summary: the use of an entire ECU as the runtime environment for the controller offers
the advantage that the necessary hardware and software infrastructure for the plant exists.
The disadvantage lies in the high degree of complexity. The concept of bypassing was devel
oped to exploit the advantages of the ECU infrastructure without being burdened by the
disadvantages of high complexity.
4.5 Bypassing
When bypassing occurs, data is recorded from the ECU and processed outside the ECU, and
the result is written back to the ECU. As both measurement and writing to the ECU must
occur in sync with the ECU processes, DAQ and STIM mechanisms are used. At least two
DAQ lists are required, one with the DAQ direction (from Slave to Master) and one with the
STIM direction (from Master to Slave).
In Figure 70, the ECU is connected to the plant. The necessary I/O and software compo
nents are available in the ECU. In the bypassing hardware, an algorithm A1 runs, which
occurs in Version A of the ECU. A1 is a new variant of the algorithm and should now be tried
out on the real plant.
4.5 Bypassing
99
ECU
A2L
XCP
Bypassing Hardware
CANape
Bypassing
Hardware
A2L
XCP
I/O
Controller Model
ECU
Plant
Figure 70: Basic principle of bypassing
The bypassing hardware (a VN8900 device in the figure) and the ECU are interconnected
over XCP. One goal here is to get the data needed for algorithm A1 from the ECU by DAQ;
another goal is to stimulate the results of A1 back into the ECU. The following figure illus
trates the schematic flow:
Bypassing Hardware
Algorithm A’
2.
Bypassing
Coordinator
3.
1. XCP 4.
Algorithm A
ECU
Figure 71:
Bypassing flow
Depicted in the ECU is a blue function block in which the algorithm A runs. To ensure that A1
can now be used, the data enters algorithm A as an input variable and it is measured from
the ECU by DAQ.
Step 1: In the ECU, the data is recorded and sent to the bypassing tool before the original
function is calculated in the ECU. Normally, the input data in functions A and A1 is are
identical.
Step 2: The data transferred via DAQ is now transferred to algorithm A1.
Step 3: The results of the calculation of algorithm A1 are transferred to the bypassing tool.
Step 4: The data is transferred into the ECU via STIM. The ECU calculates algorithm A dur
ing this time. If the stimulated results are available and calculation of algorithm A is com
100
4 Application Areas of XCP
plete, the values calculated in the ECU are typically overwritten by the stimulated values of
algorithm A1.
This makes it possible to use the value computed by algorithm A1 and not from A in the
ECU’s overall control process. This method permits using a combination of the rapid substi
tution of algorithms on the bypassing hardware that incorporates the I/O and the ECU’s
basic software.
Of course, performance limits of the transport protocol also affect bypassing. If short
bypassing times are needed, access to the ECU by DAQ and STIM may also be performed via
the controller’s debugging or trace interfaces. The Vector VX1000 measurement and cali
bration hardware converts the data into an XCPonEthernet data stream from the control
ler interface. In this process, up to one megabyte of data can be transported into the ECU.
XCP
Bypassing Hardware
Bypassing
CANape
Hardware
A2L
XCP
Measurement & Calibration
Hardware VX1000
Debugging and
Trace Interface
I/O
Controller Model
ECU
Plant
Figure 72: Bypassing with real-time bypassing hardware and fast ECU access
In the figure, ECU access occurs via XCP on Ethernet, and calculation of the bypass algo
rithm occurs on separate bypassing hardware (VN8900 network interface) with a realtime
operating system. This means that the variance of the calculation time is considerably
smaller than with calculation on a laptop, as the processing time is not affected by other
applications.
4.6 Shortening Iteration Cycles with Virtual ECUs
101
4.6 Shortening Iteration Cycles with Virtual ECUs
Stimulation with data is necessary to optimize the algorithm in the ECU with the help of
XCP. This can be done in the ECU in the framework of test drives. But there is yet another
solution that is available with XCP, in which the algorithm does not run on an ECU; rather it
runs on the PC in the form of executable code or as a model in Simulink in the form of a
“virtual ECU.” This virtual ECU does not need to run in real time, because in this case no con
nection to a real system exists. It can run significantly faster – depending on the PC’s com
puting power.
The algorithm is stimulated by a previously logged measurement file, which contains all
signals that are needed as input signals for the algorithm. The connection to CANape is set
up over XCP. The user can perform the parameterization and measurement configuration.
Afterwards, execution is started. Here the data from the test drive is fed into the algorithm
as stimulation and the desired measurement parameters from the application are simulta
neously measured out and saved to a measurement file.
Para-
MDF
meter
test drive
Application
5. Analyze
1. Set parameters
2. Start
Simulink/
CANape
DLL
3. Send test drive data
4. Measurement data
Slave
New
MDF
Figure 73:
Short calibration cycles
with virtual ECUs
102
4 Application Areas of XCP
After the calculation has been completed, a new measurement file is available to the user
for analysis of ECU behavior. The length of time of the new measurement file precisely
matches the length of the input measurement file. If the duration of a test drive is one hour,
the algorithm on the PC might calculate the entire test drive in just a few seconds. Then a
measurement result exists, which corresponds to a test of one hour duration. Based on the
data analysis, the user makes decisions about parameterization and the iteration cycle is
repeated.
CANape
Application as EXE or DLL on PC
Parameterization
Set values in
via XCP
workspace
Start
Start
Send measurement
Calculate model
data
Receive new
Send measurement
measurement data
values from the model
Analyze the
End model calculation
new data
New software version
Figure 74:
Process flow with
virtual ECUs
To shorten the iteration cycles, the algorithm is always stimulated with the same data. That
makes the results with different parameters much more comparable, because the results
are only influenced by the parameters that differ.
This process can of course be automated. The integrated script language of CANape per
forms an analysis of the measurement results, from which parameter calibration settings
are derived and automatically executed. It is also possible to have the process controlled by
an external optimization tool such as MATLAB over the CANape automation interface.
5 Example of an XCP Implementation
105
5 Example of an XCP Implementation
106
5 Example of an XCP Implementation
To make it possible for an ECU to communicate over XCP, it is necessary to integrate an XCP
driver in the ECU’s application. The example described below is of the XCP driver which you
can download free of charge at the Download Center of the Vector website (www.vector.
com/xcpdriver). This packet also contains some sample implementations for various trans
port layers and target platforms. The driver consists of the protocolLayer with the basic
functionality needed for measurement and calibration. It does not include features such as
Cold Start Measurement, Stimulation or flashing. You can purchase a full implementation
as a product that is integrated in the Vector CANbedded or AUTOSAR environment.
The XCP protocol layer is placed over the XCP transport layer, which in turn is based on the
actual bus communication. The implementation of the XCP protocol layer only consists of a
single C file and a few H files (xcpBasix.c, xcpBasic.h, xcp_def.h and xcp_cfg.h). The examples
include implementations for various transport layers, e.g. Ethernet and RS232. In the case of
CAN, the transport layer is normally very simple and the various XCP message types are
mapped directly to CAN messages. There are then separate fixed identifiers for the Tx and
Rx directions.
The software interface between the transport and protocol layers is very simple. It contains
just a few functions:
> When the Slave receives an XCP message over the bus, it first arrives in the communica
tion driver, which routes the message to the XCP transport layer. The transport layer
informs the protocol layer about the message with the function call XcpCommand().
> If the XCP protocol layer wishes to send a message (e.g. a response to an XCP command
from the Master or a DAQ message), the message is routed to the transport layer by a call
of the ApplXcpSend() function.
> The transport layer informs the protocol layer that the message was successfully sent by
the function call XcpSendCallBack().
5 Example of an XCP Implementation
107
Application
ointer
etP
vent
ackground
cpG
cpE
cpInit
cpB
pplX
X
X
X
A
XCP Protocol Layer
and
end
alback
pplication – XCP Transport Layer Interface
m
A
cpS
om
endC
pplX
cpC
A
cpS
X
X
XCP Transport Layer
Physical Layer
Figure 75:
Incorporating
Bus
the XCP Slave
in the ECU code
The interface between the application and the protocol layer can only be implemented via
four functions:
> The application activates the XCP driver with the help of XcpInit(). This call is made once
in the starting process.
> With XcpEvent(), the application informs the XCP driver that a certain event has occurred
(e.g. “End of a computational cycle reached”).
> The call XcpBackground() lets the XCP driver execute certain activities in background (e.g.
calculation of a checksum).
> Since the addresses in A2L files are always defined as 40bit values (32bit address, 8bit
address extension), the XCP driver uses the function ApplXcpGetPointer() to obtain a
pointer from a A2Lconformant address.
These interfaces are sufficient to integrate basic functionalities for measurement and cali
bration. Other interfaces are only needed for extended functions such as page switching,
identification or seed & key. They are described in detail in documentation for the driver.
108
5 Example of an XCP Implementation
5.1 Description of Functions
void XcpInit (void)
Task:
Initialize the XCP driver.
Description:
The application activates the XCP driver with XcpInit(). This command must be executed
exactly once before any sort of XCP driver function may be called.
void XcpEvent (BYTE event)
Task:
The application informs the XCP driver about which event occurred. A unique event number
is assigned to each event here.
Description:
In setting up the measurement configuration in the measurement and calibration tool, the
user selects which measured values should be synchronously acquired with which events. The
information on measured values and events originates from the A2L. The desired measure
ment configuration is communicated to the XCP driver in the form of DAQ lists.
Example of an event definition in an engine controller:
XcpEvent (1);
// Event 1 stands for the 10ms task
XcpEvent (2);
// Event 2 stands for the 100ms task
XcpEvent (5);
// Event 5 stands for the 1ms task
XcpEvent (8);
// Event 8 is used for ignition angle synchronous measurements
BYTE XcpBackground (void)
Task:
Execute background activities of the XCP driver.
Description:
This function should be called periodically in a background or idle task. It is used by the
XCP driver, for example, to compute the checksum, because the computation of a longer
checksum in XcpCommand() could take an unacceptably long time. With each call of
XcpBackground(), a partial checksum of 256 bytes is computed. The duration of a checksum
computation therefore depends on the call frequency of XcpBackground(). There are no
other requirements for the call frequency or periodicity. The return value 1 indicates that a
checksum computation is currently running.
5.1 Description of Functions
109
void XcpCommand (DWORD* pCommand)
Task:
Interpret an XCP command.
Description:
This function must be called each time the transport layer receives a XCP frame. The para
meter is a pointer to the frame.
void ApplXcpSend (BYTE len, BYTE *msg)
Task:
Transfer a frame to be sent to the transport layer.
Description:
With this call, the protocol layer sends a message to the transport layer for transmission to
the Master. The call XcpSendCallBack implements a handshake method between the proto
col and transport layers.
BYTE XcpSendCallBack (void)
Task:
The protocol layer uses this callback to inform the transport layer that the last message
that was transferred to ApplXcpSend() was successfully transmitted.
Description:
The protocol layer does not call an ApplXcpSend() command until XcpSendCallBack() indi
cates that the prior message was successfully transmitted. XcpSendCallBack() returns the
value 0 (FALSE) if the XCP driver is in idle. If there are more frames to be sent, ApplX
cpSend() is called directly from XcpSendCallBack().
BYTE *ApplXcpGetPointer (BYTE addr_ext, DWORD addr)
Task:
Convert an A2Lconformant address to a pointer.
Description:
The function maps the 40bit A2Lconformant addressing (32bit address + 8bit address
extension) that is sent by the XCP Master to a valid pointer. The address extension can be
used, for example, to distinguish different address areas or memory types.
110
5 Example of an XCP Implementation
5.2 Parameterization of the Driver
In many respects, the XCP driver is scalable and parameterizable to properly handle the
wide variety of functional content, transport protocols and target platforms. All settings are
made in the parameter file xcp_cfg.h. In the simplest case, they appear as follows:
/* Define protocol parameters */
#define kXcpMaxCTO 8 /* Maximum CTO Message Length */
#define kXcpMaxDTO 8 /* Maximum DTO Message Length */
#define C_CPUTYPE_BIGENDIAN /* byte order Motorola */
/* Enable memory checksum */
#define XCP_ENABLE_CHECKSUM
#define kXcpChecksumMethod XCP_CHECKSUM_TYPE_ADD14
/* Enable calibration */
#define XCP_ENABLE_CALIBRATION
#define XCP_ENABLE_SHORT_UPLOAD
/* Enable data acquisition */
#define XCP_ENABLE_DAQ
#define kXcpDaqMemSize (512) /* Memory space reserved for DAQ */
#define XCP_ENABLE_SEND_QUEUE
For a CAN transport layer, the appropriate CTO and DTO parameters of eight bytes are set.
The driver must know whether it is running on a platform with Motorola or Intel byte order,
in this case a MotorolaCPU (Big Endian). The remaining parameters activate the function
alities: measurement, calibration and checksum computation. The algorithm for checksum
computation is configured (here summing of all bytes into a DWORD) and the parameter of
the available memory is indicated for the measurement (here 512 bytes). The memory is pri
marily needed to store the DAQ lists and to buffer the data during the measurement. The
parameter therefore determines the maximum possible number of measurement signals. In
the driver documentation you will find more detailed information on estimating the neces
sary parameters.
6 Protocol Development Overview
111
6 Protocol Development Overview
112
6 Protocol Development Overview
The following overview shows some of the essential developments of the XCP protocol,
which was standardized in 2003.
6.1. XCP Version 1.1 (2008)
> Description of the same XCP interface using two different physical interfaces within the
same A2L (e.g. “XCP on Vehicle CAN” and “XCP on Calibration CAN”)
> The new command WRITE_DAQ_MULTIPLE makes it possible to accelerate configuration
of the Slave. Two ODTs appearing in succession in a DAQ list can be communicated in a
single step.
> High time synchronization via “TIMESTAMP_EVENT.” Timestamp information is communi
cated by the Slave. The trigger can be initiated via an external synchronization cable.
> Compression of embedded A2L files
All expansions are optional. XCP 1.1 is thus compatible with XCP 1.0.
6.2. XCP Version 1.2 (2013)
> Parameters in the A2L for the definition of the required ECU resources via XCPDAQ mea
surement configurations (e.g. RAM usage, CPU execution time and required transfer band
width for CAN or Ethernet). The XCP Master can access the parameters, calculate
resource usage for the measurement and warn the user if overshooting occurs.
> Prioritization control by the Master for transfer of the measurement data via CAN. The
objective here is to not disturb the necessary communication flow of the vehicle CAN to
the greatest degree possible.
> Calculation of the required bandwidth and limits for the transfer of data via TCP or UDP
> Description of XCP on CAN FD
All expansions are optional. XCP 1.2 is thus compatible with XCP 1.1.
6.3. XCP Version 1.3 (2015)
113
6.3. XCP Version 1.3 (2015)
> Improvement of the time correlation of XCP Slaves using multicast solutions found on the
same network
> Time synchronization between XCP Slave timestamp and external clock, e.g. via IEEE 1588
> Checking of the bypassing data flow and error handling
All expansions are optional. XCP 1.3 is thus compatible with XCP 1.2.
114
The Authors
The Authors
Andreas Patzer
Mr. Patzer graduated in Electrical Engineering from the Technical University of
Karlsruhe. In his studies he specialized in measurement and control engineering
and information and industrial engineering. In 2003, he joined Vector Informatik
GmbH in Stuttgart. Andreas Patzer has supported XCP projects from the very
start, since XCP was standardized by ASAM e.V. in the same year he was hired.
He currently manages the Customer Relations and Services area as a team
leader for the Measurement & Calibration product line.
The Authors
115
Rainer Zaiser
Mr. Zaiser has a degree in Electrical Engineering from the University of
Stuttgart. After graduating, he came directly to Vector Informatik GmbH in
autumn 1988, where he has helped to create many of the standards that have
become established in the automotive industry such as DBC, MDF, CCP, A2L
and to a large extent XCP. From the start, he headed up the Measurement &
Calibration and Network Interfaces product lines.
116
Table of Abbreviations and Acronyms
Table of Abbreviations and Acronyms
A2L
File extension for an ASAM 2MC language file
AML
ASAM 2 Meta Language
ASAM
Association for Standardisation of Automation and Measuring Systems
BYP
Bypassing
CAL
Calibration
CAN
Controller Area Network
CCP
CAN Calibration Protocol
CMD
Command
CS
Checksum
CTO
Command Transfer Object
CTR
Counter
DAQ
Data Acquisition, Data Acquisition Packet
DTO
Data Transfer Object
ECU
Electronic Control Unit
ERR
Error Packet
EV
Event Packet
FIBEX
Field Bus Exchange Format
LEN
Length
MCD
Measurement Calibration and Diagnostics
MTA
Memory Transfer Address
ODT
Object Descriptor Table
PAG
Paging
PGM
Programming
PHY
Physical Layer respectively description of the chip connecting a link layer
device to a physical medium, for example Ethernet PHY
PID
Packet Identifier
PTP
Precision Time Protocol
RES
Command Response Packet
SERV
Service Request Packet
SPI
Serial Peripheral Interface
STD
Standard
STIM
Data Stimulation Packet
TCP/IP
Transfer Control Protocol / Internet Protocol
TS
Timestamp
UDP/IP
Unified Data Protocol / Internet Protocol
USB
Universal Serial Bus
XCP
Universal Measurement and Calibration Protocol
Download
Sending of data from Master to Slave
Upload
Sending of data from Slave to Master
Literature & Web Addresses
117
Literature
XCP is specified by ASAM (Association for Standardisation of Automation and Measuring
Systems).
You will find details on the protocol and on ASAM at: www.asam.net
Web Addresses
Standardization committees:
> ASAM, XCP protocolspecific documents, A2L specification, www.asam.net
Supplier of development software:
> MathWorks, information on MATLAB, Simulink and Simulink Coder, www.mathworks.com
> Vector Informatik GmbH, demo version of CANape, free of charge and openly available
XCP driver (basic version), comprehensive information on the topics of ECU calibration,
testing and simulation, www.vector.com
118
Table of Figures
Table of Figures
Figure 1: Fundamental communication with a runtime environment ..........................................8
Figure 2: The Interface Model of ASAM............................................................................................... 9
Figure 3: An XCP Master can simultaneously communicate with multiple Slaves ..................10
Figure 4: Subdivision of the XCP protocol into protocol layer and transport layer ................14
Figure 5: XCP Slaves can be used in many different runtime environments ............................15
Figure 6: XCP packet ..............................................................................................................................19
Figure 7: Overview of XCP Packet Identifier (PID) .........................................................................19
Figure 8: XCP communication model with CTO/DTO ....................................................................20
Figure 9: Message identification .........................................................................................................21
Figure 10: Timestamp ............................................................................................................................21
Figure 11: Data field in the XCP packet ............................................................................................22
Figure 12: The three modes of the XCP protocol: Standard, Block and Interleaved mode ...24
Figure 13: Overview of the CTO packet structure ..........................................................................25
Figure 14: Trace example from a calibration process .....................................................................30
Figure 15: Transfer of a parameter set file to an ECU’s RAM .....................................................31
Figure 16: Hex window ..........................................................................................................................32
Figure 17: Address information of the parameter “Triangle” from the A2L file ......................33
Figure 18: Polling communication in the CANape Trace window ................................................34
Figure 19: Events in the ECU ...............................................................................................................35
Figure 20: Event definition in an A2L .................................................................................................35
Figure 21: Allocation of “Triangle” to possible events in the A2L ................................................36
Figure 22: Selecting events (measurement mode) for each measurement parameter .........36
Figure 23: Excerpt from the CANape Trace window of a DAQ measurement .........................37
Figure 24: ODT: Allocation of RAM addresses to DAQ DTO .........................................................38
Figure 25: DAQ list with three ODTs ..................................................................................................39
Figure 26: Static DAQ lists ...................................................................................................................40
Figure 27: Dynamic DAQ lists ..............................................................................................................41
Figure 28: Event for DAQ and STIM ...................................................................................................42
Figure 29: Structure of the XCP packet for DTO transmissions..................................................43
Figure 30: Identification field with absolute ODT numbers ..........................................................44
Figure 31: ID field with relative ODT and absolute DAQ numbers (one byte) .........................44
Figure 32: ID field with relative ODT and absolute DAQ numbers (two bytes) ......................44
Figure 33: ID field with relative ODT and absolute DAQ numbers as well as fill byte
(total of four bytes) ............................................................................................................45
Figure 34: XCP Slave with freerunning clock .................................................................................46
Figure 35: The clock of the XCP Slave is synchronized with the grandmaster clock .............47
Figure 36: Definition of which bus nodes send which messages .................................................49
Figure 37: Representation of a CAN network ..................................................................................50
Figure 38: Example of XCPonCAN communication .....................................................................51
Figure 39: Representation of an XCPonCAN message ...............................................................51
Figure 40: Illustration of a CAN FD frame ........................................................................................52
Figure 41: Nodes K and L are redundantly interconnected ...........................................................54
Figure 42: Communication by slot definition ...................................................................................54
Figure 43: Representation of a FlexRay communication matrix..................................................55
Figure 44: Representation of the FlexRay LPDUs ...........................................................................56
Table of Figures
119
Figure 45: Allocation of XCP communication to LPDUs ................................................................57
Figure 46: XCP packet with TCP/IP or UDP/IP ................................................................................58
Figure 47: XCPonSxI packet ..............................................................................................................59
Figure 48: Memory representation .....................................................................................................61
Figure 49: Representation of driver settings for the flash area ..................................................63
Figure 50: Representation of the block transfer mode ..................................................................66
Figure 51: Parameters in a calibration window ...............................................................................72
Figure 52: Signal response over time .................................................................................................72
Figure 53: Initial parameter setting in RAM .....................................................................................82
Figure 54: Initial situation after booting ...........................................................................................86
Figure 55: Pointer change and copying to RAM ..............................................................................87
Figure 56: Pointer table for individual parameters .........................................................................87
Figure 57: Double pointer concept ......................................................................................................89
Figure 58: Application areas and application cases .......................................................................92
Figure 59: Plants and controllers ........................................................................................................92
Figure 60: Model in the Loop in Simulink ..........................................................................................93
Figure 61: CANape as measurement and calibration tool with Simulink models ...................93
Figure 62: Software in the Loop with Simulink environment .......................................................94
Figure 63: CANape as SIL development platform ..........................................................................94
Figure 64: HIL solution ...........................................................................................................................95
Figure 65: HIL with CANape as measurement and calibration tool ...........................................95
Figure 66: CANoe as HIL system .........................................................................................................96
Figure 67: CANoe as HIL system with XCP access to the ECU ...................................................96
Figure 68: CANape as HIL solution .....................................................................................................97
Figure 69: RCP solution .........................................................................................................................97
Figure 70: Basic principle of bypassing ..............................................................................................99
Figure 71: Bypassing flow .....................................................................................................................99
Figure 72: Bypassing with realtime bypassing hardware and fast ECU access ................. 100
Figure 73: Short calibration cycles with virtual ECUs ................................................................. 101
Figure 74: Process flow with virtual ECUs ..................................................................................... 102
Figure 75: Incorporating the XCP Slave in the ECU code .......................................................... 107
120
Appendix – XCP Solutions at Vector
Appendix – XCP Solutions at Vector
Vector made a significant effort in giving shape to the XCP standard. Its extensive know
how and vast experience were utilized to provide comprehensive XCP support:
Tools
> The primary use area of CANape is in optimal parameterization (calibration) of electronic
control units (ECUs). During the system’s runtime, you calibrate parameter values and
simultaneously acquire measured signals. The physical interface between CANape and the
ECU is over XCP (for all standardized transport protocols) or CCP.
> Complete tool chain for generating and managing the necessary A2L description files
(ASAP2 Tool-Set and CANape with the ASAP2 Editor).
> You use CANoe.XCP to access internal ECU values for testing and analysis tasks.
ECU Interfaces
The VX1000 measurement and calibration hardware offers the option of equipping ECUs
with an XCPonEthernet interface. This involves connecting a Plug on Device (POD) to the
ECU for direct access to the controller, e.g. over DAP, JTAG, Nexus, etc. The POD transmits
the data to a base module, which operates as an XCP Slave and provides the data to the
XCP Master on the PC over XCP on Ethernet. This makes it unnecessary to have an XCP
Slave in the ECU. The user benefits from a high measurement data throughput rate of up to
50 MByte/s and short measurement intervals of less than 15 µs.
Embedded Software
Communication modules with separate transport layers for CAN, FlexRay and Ethernet:
> XCP Basic – free download at www.vector.com/xcpdriver, only contains basic XCP func
tions. Configuration of the XCP protocol and modification of the transport layer are per
formed manually in the source code. You need to integrate XCP Basic in your project
yourself.
> XCP Professional – contains useful extensions to the ASAM specification and enables tool
based configuration. Available for Vector CANbedded basic software.
> MICROSAR XCP – contains the functional features of XCP Professional and is based on
AUTOSAR specifications. Available for Vector MICROSAR basic software.
Services
> Consultation for using XCP in your projects
> Integration of XCP in your ECU
Training
> You can learn about the underlying mechanisms and models of the protocol in the “XCP
Fundamentals Seminar”.
> In the “CANape with XCP on FlexRay Workshop” you learn about FlexRay fundamentals
and the special aspects of XCP on FlexRay are explained, in particular dynamic bandwidth
management.
Special XCP Support by CANape
121
Special XCP Support by CANape
CANape was the first MCD tool to support the XCP 1.0 specification and was also the first
XCP on FlexRay Master on the market.
A special technical feature of XCP on FlexRay is dynamic bandwidth management. Here,
CANape identifies the available bandwidth provided for XCP in the FlexRay ClusterP and it
allocates this bandwidth to the momentary application data traffic dynamically and very
efficiently. The available bandwidth is thereby optimally used for XCP communication.
Moreover, CANape has a DLL interface. It enables support of XCP on any desired (user
defined) transport layer. This lets you integrate any desired test instrumentation or proprie
tary protocols in CANape. A code generator supports you in creating the XCPspecific share
of such a driver.
122
Index
Index
A
F
A2L
9, 10, 25, 35, 40, 42, 56, 57, 62, 63, 68, FIBEX
55 – 57
71 – 76, 94, 108, 109, 116
Flash memory
16, 17, 61 – 64, 67
Address extension
29, 33, 38, 107, 109
FLX_CHANNEL
56
AML
25, 74, 116
FLX_LPDU_ID
56
ASAM
7 – 9, 60, 116
FLX_SLOT_ID
56
ASAP2 ToolSet
76
Fullpassing
98
B
G
Bandwith optimization
34
GET_CAL_PAGE
25, 62
Bus load
34
GET_DAQ_EVENT_INFO
65, 77
BYP
116
GET_DAQ_LIST_INFO
77
Bypassing
45, 98, 100
GET_DAQ_PROCESSOR_INFO
45, 65, 77
GET_DAQ_RESOLUTION_INFO
65, 77
C
Grandmaster clock
47, 48
CAN
7, 8, 14, 24, 29, 33, 38, 49, 50, 51, 55,
75, 116
H
CAN FD
52
HIL
92, 95 – 97
CCP
7, 8, 40, 49, 116
CMD
25, 56, 116
I
CTO
21, 22, 25, 116
IEEE 1588
47
CTR
58, 59, 116
IF_DATA
25
CYCLE_REPETITION
56
K
D
Commands
25
DAQ
22, 32 – 45, 65, 67, 77, 99, 100, 106, Compile
76, 80, 82, 94
108, 116
DAQ_KEY_BYTE
45
L
DBC
49
Linking
80, 94
Double Pointer Concept
88
LPDU
56
DOWNLOAD
30, 31, 66
DTO
21, 22, 33, 37, 116
M
Maturity level
31
E
MIL
93
ECU
9, 74, 98, 99, 116
MTA
30, 116
ECU description file A2L
72 – 77
Multicast 46,
113
EEPROM
16, 31, 67
ERR
25, 28, 116
O
Ethernet 57 – 59
ODT
37 – 41, 43, 44, 65, 77, 116
EV
29, 116
OFFSET
56
Event
35, 38 – 40, 42,65, 67, 77, 108
Index
123
P
PAG
116
Page
61 – 63
Page switching
62, 63
Parameter
85
PGM
116
PID
8, 19, 21, 25, 43, 116
Polling
33, 34, 36
PTP
47
R
RAM
16 – 18, 30, 31, 37, 39, 63, 67, 80, 82,
85, 86, 88
Reboot
32
RES
21, 28, 56, 116
S
Sector
61 – 63
Segment
61 – 63
SEGMENT_NUMBER
62
SERV
29, 116
SET_CAL_PAGE
25, 62
SET_MTA
30
SHORT_UPLOAD
30, 33, 66
SIL
92, 94
Single Pointer Concept
86
STIM
33, 42, 43, 45, 65, 77, 100, 116
Stimulation
29, 68, 101
T
Task
108
TCP/IP
57, 58, 116
U
UDP/IP
57, 58, 116
USB
60, 116
V
Virtual ECU
101
Volatile 81, 82
VX1000
100
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V3.
Document Outline
- Table of Contents
- Introduction
- 1 Fundamentals of the XCP Protocol
- 2 ECU Description File A2L
- 3 Calibration Concepts
- 4 Application Areas of XCP
- 5 Example of an XCP Implementation
- 6 Protocol Development Overview
- The Authors
- Table of Abbreviations and Acronyms
- Literature & Web Addresses
- Table of Figures
- Appendix – XCP Solutions at Vector
- Index