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 purpose of the Tx Passive Mode (Listen‑Only Mode) on my CAN interface board or analysis tool?
ANSWER
When a CAN controller receives a message on the bus, it automatically sends an acknowledgment (ACK), even if the message is not intended for that specific device. This ACK lets the transmitting node know that the message was successfully placed on the bus. However, it does not guarantee that the intended recipient received the message without errors.
A PC-based CAN interface board typically sends an ACK for every received message. This behavior can unintentionally influence the CAN network, potentially masking communication errors during analysis.
To avoid such interference, the Tx passive mode (also known as Listen-only mode) can be activated. In this mode, the interface board only listens to the bus traffic without sending any acknowledgments. This ensures that the analysis tool does not affect the network behavior, allowing for accurate diagnostics and error detection.
© HMS Networks AB 2022