Datasheet

Figure 49-3. Pin Control in Bus Monitoring Mode
CANTX CANRX
Tx Rx
MCAN
•
•
=1
Bus Monitoring Mode
49.5.1.7 Disabled Automatic Retransmission
According to the CAN Specification (see ISO11898-1, 6.3.3 Recovery Management), the MCAN 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. T
o support time-triggered communication as described
in ISO 11898-1, chapter 9.2, the automatic retransmission may be disabled via MCAN_CCCR.DAR.
49.5.1.7.1 Frame Transmission in DAR Mode
In DAR mode, all transmissions are automatically cancelled after they start 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 MCAN_TXBTO.TOx set
Corresponding Tx Buffer Cancellation Finished bit MCAN_TXBCF.CFx not set
• Successful transmission in spite of cancellation:
Corresponding Tx Buffer Transmission Occurred bit MCAN_TXBTO.TOx set
Corresponding Tx Buffer Cancellation Finished bit MCAN_TXBCF.CFx set
• Arbitration lost or frame transmission disturbed:
Corresponding Tx Buffer Transmission Occurred bit MCAN_TXBTO.TOx not set
Corresponding Tx Buffer Cancellation Finished bit MCAN_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).
49.5.1.8 Power-down (Sleep Mode)
The MCAN can be set into Power-down mode via bit MCAN_CCCR.CSR.
When all pending transmission requests have completed, the MCAN waits until bus idle state is detected. Then the
MCAN sets MCAN_CCCR.INIT to prevent any further CAN transfers. Now the MCAN acknowledges that it is ready
for power down by setting to one the bit MCAN_CCCR.CSA. In this state, before the clocks are switched of
f, further
register accesses can be made. A write access to MCAN_CCCR.INIT will have no effect. Now the bus clock
(peripheral clock) and the CAN core clock may be switched off.
To leave Power-down mode, the application has to turn on the MCAN clocks before clearing CC Control Register flag
MCAN_CCCR.CSR. The MCAN will acknowledge this by clearing MCAN_CCCR.CSA. The application can then
restart CAN communication by clearing the bit CCCR.INIT.
49.5.1.9 Test Modes
To enable write access to the MCAN Test register (MCAN_TEST) (see Section 7.6), bit MCAN_CCCR.TEST must be
set. This allows the configuration of the test modes and test functions.
Four output functions are available for the CAN transmit pin CANTX by programming MCAN_TEST.TX. Additionally
to its default function – the serial data output – it can drive the CAN Sample Point signal to monitor the MCAN’s bit
SAM E70/S70/V70/V71 Family
Controller Area Network (MCAN)
© 2019 Microchip T
echnology Inc.
Datasheet
DS60001527D-page 1410