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TJA1145A err flag PNFDE cannot recover

Hi, NXP expert

I use the TJA1145A as the transceiver of the can bus. when I make the CANH connected to GND to test bus off, I found the PNFDE bit is =1. but why the PNFDE flag can not recover even if the bus off disappear and communication is normal. how should I do with the transceiver after the bus off recover.

Re: TJA1145A err flag PNFDE cannot recover

Hi,

Please accept our sincere apologies for the delay in responding to your question, it appears that it was overlooked.

The PNFDE bit is a latched status flag. It is set when the internal error counter overflows while the device is monitoring for wake-up frames. This flag does not clear automatically when the bus returns to normal operation, it must be cleared by the MCU.

How to clear PNFDE:
- Read the Transceiver Event Status Register (address 0x63).
- Write a 1 to the PNFDE bit to clear it (writing 0 has no effect).

After clearing, normal operation can continue. No additional reset of the transceiver is required.

BRs, Tomas