SWRU626 December 2025 CC3501E , CC3551E
The DCAN can be set in External Loop Back Mode by programming TEST.LBCK to one. In Loop Back Mode, the DCAN treats its own transmitted messages as received messages and stores them (if they pass acceptance filtering) into an Rx Buffer or an Rx FIFO. shows the connection of signals m_can_tx and m_can_rx to the DCAN in External Loop Back Mode.
This mode is provided for hardware self-test. To be independent from external stimulation, the DCAN ignores acknowledge errors (recessive bit sampled in the acknowledge slot of a data/remote frame) in Loop Back Mode. In this mode the DCAN performs an internal feedback from its Tx output to its Rx input. The actual value of the DCAN_RX input pin is disregarded by the DCAN. The transmitted messages can be monitored at the DCAN_TX pin.