6.8 Retransmission in DAR mode due to lost arbitration at the first two identifier bits

Attention: This erratum is applicable for CAN 2.0.

When the MCAN is configured in DAR mode (MCAN_CCCR.DAR = ’1’) the Automatic Retransmission for transmitted messages that have been disturbed by an error or have lost arbitration is disabled. When the transmission attempt is not successful, the Tx Buffer’s transmission request bit (MCAN_TXBRP.TRPxx) shall be cleared and its Cancellation Finished bit (MCAN_TXBCF.CFxx) shall be set.

When the transmitted message loses arbitration at one of the first two identifier bits, it may happen that instead of the bits of the actually transmitted Tx Buffer, the MCAN_TXBRP.TRPxx and MCAN_TXBCF.CFxx bits of the previously started Tx Buffer (or Tx Buffer 0 if there is no previous transmission attempt) are written (MCAN_TXBRP.TRPxx = ’0’, MCAN_TXBCF.CFxx = ’1’).

If in this case the MCAN_TXBRP.TRPxx bit of the Tx Buffer that lost arbitration at the first two identifier bits has not been cleared, retransmission is attempted.

When the MCAN loses arbitration again at the immediately following retransmission, then actually and previously transmitted Tx Buffers are the same and this Tx Buffer’s MCAN_TXBRP.TRPxx bit is cleared and its MCAN_TXBCF.CFxx bit is set.

Work around

None