Fujitsu MB90895 Series Hardware Manual page 555

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Starting transmission
Setting of transmission request
To start transmitting, set the TREQx bit in the transmission request register to "1" which corresponding
to the message buffer (x) that transmits the message.When the TREQx bit is set, the transmission
complete register is cleared (TCR: TCx = 0).
Presence or absence of remote frame receive wait
If the RFWTx bit in the remote frame receive wait register is set, transmitting is started after a remote
frame is received (RRTRR: RRTRx = 1).If the remote frame receive wait register does not wait for
receiving of a remote frame (RFWTR: RFWTx = 0), transmitting is started immediately after the
transmission request bit is set (TREQR: TREQx = 1).
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Transmission operation
Transmission request set in more than one message buffer
When a transmission request is set in more than one message buffer (TREQR: TREQx = 1),
transmitting is performed starting with the small-numbered message buffer (x = 7 to 0).
Transmitting to CAN bus
Transmitting message to the CAN bus from the transmit output pin (TX) is started when the CAN bus is
idle.
Arbitration
Arbitration is performed when the CAN controller causes contention for a message buffer with another
transmitting CAN controller on the CAN bus.If arbitration fails or an error occurs during transmitting,
retransmitting is performed automatically until it succeeds after waiting until the bus goes idle again.
Selection of frame format
When "0" is set to the TRTRx bit in the transmit RTR register, a data frame is transmitted.When "1" is
set to the bit, a remote frame is transmitted.
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Canceling transmit request
Cancellation by transmission cancel register (TCANR)
During message transmission, the transmission request set in the message buffer that is not transmitted
(held) can be cancelled by setting "1" in the transmission cancel register (TCANR).
When the transmission request is completely cancelled (TCANR: TCANx = 1), the transmission request
register is cleared (TREQx = 1).
Cancellation by receiving message
The message buffer can receive the message even during requesting a transmission. However, the
transmission request is cancelled under the following conditions:
Request to transmit data frame:
When a data frame is received, the transmission request is cancelled.When a remote frame is received,
the transmission request is not cancelled.
Request to transmit remote frame:
The transmission request is cancelled even if either a data frame or remote frame is received.
CHAPTER 16 CAN controller
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