Tx Rx
CAN Core
DCAN
CAN_RX
CAN_TX
Test Modes
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SPNU563A–March 2018
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Controller Area Network (DCAN) Module
27.14.2 Loop Back Mode
The Loop Back 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 still can be monitored at the CAN_TX
pin.
In order 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 Loop Back Mode.
Figure 27-17 shows the connection of signals CAN_TX and CAN_RX to the CAN Core in Loop Back
Mode.
Loop Back Mode can be activated by setting bit LBack in Test Register to 1.
NOTE: In Loop Back 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
External Loop Back mode (Section 27.14.3).
Figure 27-17. CAN Core in Loop Back Mode
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