SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
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 the messages pass acceptance filtering. The actual value of the CAN_RX input pin is disregarded by the CAN core. Transmitted messages still can be monitored at the CAN_TX pin.
To be independent from external stimulation, the CAN core ignores acknowledge errors (recessive bit sampled in the acknowledge slot of a data/remote frame) in loopback mode.
Figure 21-5 shows the connection of signals CAN_TX and CAN_RX to the CAN core in loopback mode. Loopback mode can be activated by setting the LBack bit in the CAN_TEST register to 1.