AN-ISC-2-1029_Transceiver_Handlings

Transceiver Handling
Version 1.2
2007-09-17
Application Note AN-ISC-2-1029

Author(s) Hussain
Darwish
Restrictions Restricted
membership
Abstract
This application note describes how to handle the transceiver before or after calling Vector's API.

Table of Contents

1.0
Introduction ......................................................................................................................................................1
2.0
Transceiver Handling .......................................................................................................................................2
2.1
Initialization....................................................................................................................................................2
2.2
Sleep Mode ...................................................................................................................................................2
2.3
Wakeup .........................................................................................................................................................2
3.0
Special Considerations ....................................................................................................................................2
3.1
Possible Deadlock.........................................................................................................................................2
3.2
Return Value of the Function CanSleep() .....................................................................................................3
4.0
CAN Communication Layer (CCL)...................................................................................................................3
5.0
Contacts...........................................................................................................................................................3

1.0 Introduction
In communications, transceivers are used to convert the voltage level of the signal to a different signal form such
as lights, frequency or even different voltage level. the appropriate bus voltage level to communicate through a
medium. to be more resistant to transient noise, and reduce the Electromagnetic Emission (EME). Transceivers
also detect collisions in the bus. There are different transceivers for different applications. For instance, the
automotive industry uses three types of transceivers:
1. High Speed Transceivers (ISO 11898-2): the most common type used in the automotive industry. They
are mostly used in power train buses and can handle baud rates up to 1Mbps.
2. Fault-Tolerant Transceivers (ISO 11898-3): used mostly in slow baud rate buses like body bus and can
handle baud rates up to 125kbps. The major advantage of this type of transceivers is that they can
communicate without errors even if one bus line gets disconnected, shorted to ground or battery. Also,
they can communicate without errors if both bus lines are shorted together. However, they cannot
communicate if both bus lines are disconnected, shorted to ground or battery. Up to 32 nodes can be
connected to the fault-tolerant bus.

Microcon
Tx
Transc
Rx
trol
eiver
STB
CANL
ler
EN
CAN

H

Figure 1: High-Speed and Fault-Tolerant Transceiver Wiring

Copyright © 2007 - Vector Informatik GmbH
1
Contact Information: www.vector-informatik.com or +49 (0)711 80670-0

Transceiver
Handling

When using Vector’s embedded software, the user has to switch the transceiver to a certain mode before or after
calling specific functions. In the following sections, the transceiver handling is explained.

2.0 Transceiver Handling
Essentially, the transceiver shall be handled in three situations:
1.  During initialization (after a reset)
2.  After putting the CAN cell into sleep mode
3.  During a wakeup

2.1 Initialization
The transceiver must be switched into Normal mode before calling the CAN driver initialization function
CanInitPowerOn(). Some CAN cells needs to monitor 11 consecutive recessive bits to initialize (or enter
configuration mode). If the CAN transceiver is not in Normal mode, it may assert the Rx line to a dominant state.
Consequently, if the transceiver is not in Normal mode and the function CanInitPowerOn() (or CanInit()) is
called, the function may not finish executing as it is waiting for 11 recessive bits to synchronize the CAN cell to the
bus. Some CAN cells do not need to monitor any recessive bit to initialize and thus the transceiver do not have to
be in Normal mode before calling the CAN driver initialization function. However, for consistency and portability
reasons, we strongly recommend that the transceiver is in Normal mode before calling the initialization function.
2.2 Sleep
Mode
When using the sleep mode feature of the CAN cell, make sure to switch the transceiver into low-power or standby
mode AFTER switching the CAN cell into sleep mode. In other words, the transceiver should be switched into low-
power or standby mode only after calling the function CanSleep(). If the function CanSleep() returns kCanFailed,
the application must not put the transceiver into low-power or standby mode.
2.3 Wakeup
When the application wants to wake up the CAN cell to transmit a message, he/she shall switch the transceiver
into Normal mode before waking the CAN cell (or calling the function CanWakeUp()), Some CAN cells cannot
wakeup properly until they monitor 11 consecutive recessive bits in the bus. If the transceiver is not in Normal
state, it may assert the Rx line to dominant state (due to a received wakeup signal from the CAN bus).
Consequently, the CanWakeUp() function may not finish executing as it is waiting for 11 recessive bits to synchronize the CAN
cell to the bus.

3.0 Special Considerations
3.1 Possible
Deadlock

Make sure that the CAN cell is in sleep mode when the transceiver is in sleep or standby mode. If the CAN cell is
not in sleep mode and the transceiver is in sleep or standby mode, activities from the bus will never be detected.
This is because the CAN cell wakes up from the sleep mode when it detects a dominant bit on the Rx pin. When
the transceiver is in sleep or standby mode, it will try to wake up the CAN cell by signaling a dominant level on the
Rx pin. From there, the microcontroller will send a wakeup event to the application and the application will switch
the transceiver into Normal mode.

On the other hand, if the transceiver is in sleep or standby mode while the CAN cell is in Normal operation mode,
the microcontroller will never detect a wakeup event as the CAN cell is not in sleep mode. Since the wakeup event

Application Note AN-ISC-2-1029

2

Transceiver
Handling

is not detected nor passed to the application (via the function ApplCanWakeUp()), the application may never be
able to switch the transceiver into Normal mode. Consequently, the application will not be able to transmit nor
receive CAN messages on the bus and may stick in a deadlock situation.
3.2  Return Value of the Function CanSleep()

As a result of the possible deadlock mentioned in the previous section, the application must check the return value
of the function CanSleep() when calling it. If CanSleep() returns kCanOk, the application can put the
transceiver into sleep or standby mode. If CanSleep() returns kCanFailed, the state of the CAN cell might be
unknown and thus the application must not put the transceiver into sleep or standby mode. In this case, the CAN
cell might be in sleep or normal operation mode depending on the hardware. What to be done if CanSleep()
returns kCanFailed is OEM specific.

Pseudocode example:

if(CanSleep() == kCanOk)
{
DeactivateTransceiver(); /* Application function to put the
transceiver into standby or
sleep mode */
}

4.0  CAN Communication Layer (CCL)

To make the implementation more consistent, Vector offers a layer called ‘Communication Control Layer (CCL)’
that takes care of transceiver handling (including initialization, sleep, wakeup, and power-off). In addition, this layer
controls all other Vector’s software layers initializations and tasks. In other words, CCL is an abstraction layer that
provides a more consistent interface to the application.

For more information on the CCL layer, please visit our website or contact us.

5.0 Contacts

Vector Informatik GmbH
Vector CANtech, Inc.
VecScan AB
Ingersheimer Straße 24
39500 Orchard Hill Pl., Ste 550
Lindholmspiren 5
70499 Stuttgart
Novi, MI 48375
402 78 Göteborg
Germany
USA
Sweden
Tel.: +49 711-80670-0
Tel: +1-248-449-9290
Tel: +46 (0)31 764 76 00
Fax: +49 711-80670-111
Fax: +1-248-449-9704
Fax: +46 (0)31 764 76 19
Email: info@vector-informatik.de
Email: info@vector-cantech.com
Email: info@vecscan.com

Application Note AN-ISC-2-1029

3

Transceiver
Handling

Vector France SAS
Vector Japan Co. Ltd.

168 Boulevard Camélinat
Seafort Square Center Bld. 18F
92240 Malakoff
2-3-12, Higashi-shinagawa,
France
Shinagawa-ku
Tel: +33 (0)1 42 31 40 00
J-140-0002 Tokyo
Fax: +33 (0)1 42 31 40 09
Tel.: +81 3 5769 6970
Email: information@vector-france.fr
Fax: +81 3 5769 6975

Email: info@vector-japan.co.jp

Application Note AN-ISC-2-1029

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Last modified July 6, 2025: Initial commit (5e3f2e6)