53.5.1.5 Restricted Operation Mode

In Restricted Operation mode, the node is able to receive data and remote frames and to give acknowledge to valid frames, but it does not send data frames, remote frames, active error frames, or overload frames. In case of an error condition or overload condition, it does not send dominant bits, instead it waits for the occurrence of bus idle condition to resynchronize itself to the CAN communication. The error counters are not incremented. The processor can set the MCAN into Restricted Operation mode by setting bit MCAN_CCCR.ASM. The bit can only be set by the processor when both MCAN_CCCR.CCE and MCAN_CCCR.INIT are set to ‘1’. The bit can be reset by the processor at any time.

Restricted Operation mode is automatically entered when the Tx Handler was not able to read data from the Message RAM in time. To leave Restricted Operation mode, the processor has to reset MCAN_CCCR.ASM.

The Restricted Operation mode can be used in applications that adapt themselves to different CAN bit rates. In this case the application tests different bit rates and leaves the Restricted Operation mode after it has received a valid frame.