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Section 20 Controller Area Network
R01UH0134EJ0400 Rev. 4.00 Page 1067 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
Message Transmission Request for Time Triggered communication
When the Time Triggered mode is used communications must fulfils the ISO11898-4
requirements.
The following procedure should be used.
Send this module to reset or halt mode
Set TCMR0 to the Init_Watch_Trigger (0xFFFF)
Enable TCMR0 compare match setting bit 10 of TTCR0
Set TCMR2 to the specified Watch_Trigger value
Keep TCMR2 compare match disabled by keeping cleared the bit 12 of TTCR0
Set CMAX to the requested value (different from 111 bin)
Set TEW to the requested value
Configure the necessary Mailboxes for Time Trigger transmission and reception
Set LAFM for the 3 LSBs of Mailbox 31
Configure MCR, BCR1 and BCR0 to the requested values
If working as a potential time master:
Set RFTROFF to the requested Init_Ref_Offset value
Set TXPR for Mailbox 30
Write H'4000 into TTTSEL
Enable the TCNTR timer through the bit 15 of TTCR0
Move to Transmission_Reception mode
Wait for the reception or transmission of a valid reference message or for TCMR0 match
If the local time reaches the value of TCMR0 the Init_Watch_Trigger is reached and the
application needs to set TXCR for Mailbox 30 and start again
If the reference message is transmitted (TXACK[30] is set) set RFTROFF to zero
If a valid reference message is received (RXPR[31] is set) then:
If 3 LSBs of ID of Mailbox 31 have high priority than the 3 LSBs of Mailbox 30 (if
working as potential time master) keep RFTROFF to Init_Ref_Offset
If 3 LSBs of ID of Mailbox 31 have lower priority than the 3 LSBs of Mailbox 30 (if
working as potential time master) decrement by 1 the value in RFTROFF
Disable TCMR0 compare match by clearing bit 10 of TTCR0
Enable TCMR2 compare match by setting bit 12 of TTCR0
Only after two reference messages have been detected on the CAN Bus (transmitted or
received) can the application set TXPR for the other Time Triggered Mailboxes.