SWRU626 December 2025 CC3501E , CC3551E
In Restricted Operation Mode, the node is able to receive data and remote frames and acknowledge 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 (ECR.REC, ECR.TEC) are frozen while Error Logging (ECR.CEL) is active. The Host can set the DCAN into Restricted Operation mode by setting bit CCCR.ASM. The bit can only be set by the Host when both CCCR.CCE and CCCR.INIT are set to ‘1’. The bit can be reset by the Host 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 Host CPU has to reset 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.
If the DCAN is connected to a Clock Calibration, CCCR.ASM is controlled by input d_can_cok. In case d_can_cok switches to ‘0’, bit CCCR.ASM is set. When d_can_cok switches back to ‘1’, bit CCCR.ASM returns to the previously written value.When there is no Clock Calibration on CAN unit connected input d_can_cok is hardwired to ‘1’.