TJA1043 Bus Off is not detecting (CANH or CANL is open)

[shanmugamsundar]

Hello All,

I need a clarification related to Bus Off detection, dependency with CAN transceiver.

Transceiver : TJA1043

Controller: Renesas RH850

During my testing on the Bus Off detection, I have observed that in the

following scenarios, Bus Off detection is not happening.

- CAN_H is connected and CAN_L is opened

- CAN_H is opened (not connected) and CAN_L is connected.

I would like to understand is there any limitation with the TJA1043 in

detecting the above scenario ?

Thanks,

Shan

tja1043‌

[shanmugamsundar]

Hello All,

I have found a FMEA matrix table from the Application hints document for TJA1043.

In that it says that if CANH or CANL is open Transmission not possible.

I have confusion, if controller tries to transmits the messages in this scenario,(i.e. CANH or CANL open), will it detect the transmit error or the No acknowledgement error.

I hope there will be a no acknowledgement error. Because if CANH or CANL is open still Controller can able to read backs the information what it has sent successfully.

Is it correct? can someone please clear my confusion.

Thanks

Shan

[shanmugamsundar · Accepted solution]

Hello All,

As per the clarification got from NXP, The CAN controller can able to read back its own sent messages even though the bus line is open.

Hence, there won't be a chance of transmit error count, only the receive error count will get increased due to no acknowledgement. So, "Bus Off" will not happen when CANH or CANL is disconnected from the network.

Thanks,

Shan