
DocID13284 Rev 2
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UM0404
CAN modules
messages and stores them (if they pass acceptance filtering) into a Receive Buffer.
shows the connection of signals
CAN_TxD
and
CAN_RxD
to the CAN Core in
Loop Back Mode.
Figure 178. CAN core in loop back mode
This mode is provided for self-test functions. 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. In this mode the CAN Core performs an internal
feedback from its Tx output to its Rx input. The actual value of the
CAN_RxD
input pin is
disregarded by the CAN Core. The transmitted messages can be monitored at the
CAN_TxD
pin.
21.7.7 Loop
back
combined with silent mode
It is also possible to combine Loop Back Mode and Silent Mode by programming bits
LBack
and
Silent
to
one
at the same time. This mode can be used for a “Hot Selftest”, meaning the
C-CAN can be tested without affecting a running CAN system connected to the pins
CAN_TxD
and
CAN_RxD
. In this mode the
CAN_RxD
pin is disconnected from the CAN
Core and the
CAN_TxD
pin is held
recessive
shows the connection of signals
CAN_TxD
and
CAN_RxD
to the CAN Core in case of the combination of Loop Back Mode
with Silent Mode.
Figure 179. CAN core in loop back combined with silent mode
CAN_TxD CAN_RxD
Tx
Rx
CAN Core
C-CAN
•
•
CAN_TxD CAN_RxD
Tx
Rx
CAN Core
C-CAN
•
•
=1