SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The loopback mode is mainly intended for hardware self-test functions. In this mode, the CAN core uses internal feedback from Tx output to Rx input. Transmitted messages are treated as received messages, and can be stored into message objects if they pass acceptance filtering. The actual value of the CAN_RX input pin is disregarded by the CAN core. Transmitted messages can still be monitored at the CAN_TX pin.
In order to be independent from external stimulation, the CAN core ignores acknowledge sampled in the acknowledge slot of a data/remote frame.
Figure 26-183 shows the connection of signals CAN_TX and CAN_RX to the CAN core in loopback mode.
Loopback mode can be activated by setting bit DCAN_TEST[4] LBACK to 1.
In loopback mode, the signal path from CAN core to Tx pin, the Tx pin itself, and the signal path from Tx pin back to CAN core are disregarded. For including these into the testing, see Section 26.10.4.12.3.3, External Loopback Mode.