performs an internal feedback from its Tx output to its Rx input. The actual value of the
input pin M_CAN_Rx is disregarded by the M_CAN. The transmitted messages can be
monitored at the pin M_CAN_Tx.
MCAN
transmit output
MCAN
receive input
MCAN
TX
RX
Figure 3-51. Pin Control in External Loopback Mode
3.5.1.9.2 Internal Loopback Mode
Internal Loopback Mode is entered by programming bits TEST[LBCK] and
CCCR[MON] to one. This mode can be used for a "Hot Selftest", meaning the M_CAN
can be tested without affecting a running CAN system connected to the pins M_CAN_Tx
and M_CAN_Rx. In this mode pin M_CAN_Rx is disconnected from the M_CAN and
pin M_CAN_Tx is held recessive. The following figure shows the connection of
M_CAN_Tx and M_CAN_Rx to the M_CAN in case of Internal Loopback Mode.
MCAN
transmit output
MCAN
receive input
=1
TX
MCAN
RX
Figure 3-52. Pin Control in Internal Loopback Mode
Functional Description
MPC5777C Reference Manual Addendum, Rev. 1, 12/2015
96 Freescale Semiconductor, Inc.
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