3.5.1.7 Disabled Automatic Retransmission
According to the CAN Specification (see ISO11898-1, 6.3.3 Recovery Management), the
M_CAN provides means for automatic retransmission of frames that have lost arbitration
or that have been disturbed by errors during transmission. By default automatic
retransmission is enabled. To support time-triggered communication as described in ISO
11898-1, chapter 9.2, the automatic retransmission may be disabled via CCCR[DAR].
3.5.1.7.1 Frame Transmission in DAR mode
In DAR mode all transmissions are automatically cancelled after they started on the CAN
bus. A Tx Buffer's Tx Request Pending bit TXBRP[TRPx] is reset after successful
transmission, when a transmission has not yet been started at the point of cancellation,
has been aborted due to lost arbitration, or when an error occurred during frame
transmission.
• Successful transmission:
• Corresponding Tx Buffer Transmission Occurred bit TXBTO[TOx] set
• Corresponding Tx Buffer Cancellation Finished bit TXBCF[CFx] not set
• Successful transmission in spite of cancellation:
• Corresponding Tx Buffer Transmission Occurred bit TXBTO[TOx] set
• Corresponding Tx Buffer Cancellation Finished bit TXBCF[CFx] set
• Arbitration lost or frame transmission disturbed:
• Corresponding Tx Buffer Transmission Occurred bit TXBTO[TOx] not set
• Corresponding Tx Buffer Cancellation Finished bit TXBCF[CFx] set
In case of a successful frame transmission, and if storage of Tx events is enabled, a Tx
Event FIFO element is written with Event Type ET = 10 (transmission in spite of
cancellation).
3.5.1.8 Power Down (Sleep Mode)
The M_CAN can be set into power down mode controlled by CC Control Register
CCCR[CSR].
When all pending transmission requests have completed, the M_CAN waits until bus idle
state is detected. Then the M_CAN sets then CCCR[INIT] to one to prevent any further
CAN transfers. Now the M_CAN acknowledges that it is ready for power down by
Functional Description
MPC5777C Reference Manual Addendum, Rev. 1, 12/2015
94 Freescale Semiconductor, Inc.
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