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Why is there a "Tx passive mode" at my CAN interface or Analysis tool?

27 Jul 2022

 

This article describes the reason for the Tx passive mode at the CAN interface or Analysis tool. 

 

APPLICABLE PRODUCTS

 CAN PC Interfaces, CAN interface board, canAnalyser V3

 

QUESTION

 
What is the reason for the Tx passive mode (Listen only mode) at my CAN interface board or Analysis tool? 
 

ANSWER

If a CAN controller receives a message on the CAN bus, it automatically sends an acknowledgment, regardless of whether the message was intended for this device or not. Due to this, the transmit node knows that the transmission was successful. However, this does not guarantee the error free reception of the message by the desired target node.

If a CAN PC interface board is connected to the CAN network, it will normally send an acknowledgment for each received message. For analyzing a CAN network and to find errors, the PC interface board should not interfere in the communication. Since this can change the network behavior and worst case cover up the error.
If "Tx passive mode" (Listen only mode) is activated, the CAN interface board will only receive messages, without sending an acknowledgment.