Fig. 23.6 Flowchart Determining Message Buffer (X) Where Receive Messages Stored - Fujitsu MB90420/5 (A) Series Hardware Manual

Figure 23.6 shows a flowchart for determining the message buffer (x) where receive messages are to be
stored. It is recommended that message buffers be arranged in the following order: message buffers in
which each AMSR bit is set to All Bits Compare, message buffers using AMR0 or AMR1, and message
buffers in which each AMSR bit is set to all bits mask.

Fig. 23.6 Flowchart Determining Message Buffer (x) where Receive Messages Stored

n Receive overrun
When the RCx bit of the reception complete register (RCR) corresponding the message buffer x to store the
receive message is set to 1, and storing the receive message of the message buffer x is completed, the
ROVRx bit of the reception complete register (ROVRR) is set to 1 and indicates the receive overrun.
n Processing for reception of data frame and remote frame
• Processing for reception of data frame
RRTRx of the remote request receiveregister (RRTRR) becomes 0.
TREQx of the transmission request register (TREQR) becomes 0 (immediately before storing the receive
message). A transmission request for message buffer (x) having not executed transmission will be
canceled.
Note: A request for transmission of either a data frame or remote frame is canceled.
• Processing for reception of remote frame
RRTRx becomes 1.
If TRTRx of the transmission RTR register (TRTRR) is 1, TREQx becomes 0. As a result, the request for
transmitting remote frame to message buffer having not executed transmission will be canceled.
Notes: • A request for data frame transmission is not canceled.
• For cancellation of a transmission request, see Figure 23.7.
n Completing reception
RCx of the reception complete register (RCR) becomes 1 after storing the received message.
If a reception interrupt is enabled (RIEx of the reception interrupt enable register (RIER) is 1), an interrupt
occurs.
Note: This CAN controller will not receive any messages transmitted by itself.
CAN CONTROLLER
Start
Are message buffers with RCx
or with and
0 AM S x . 1 AM S x . 0
found?
0 0
YES
Select the lowest-numbered
message buffer.
End
set to
NO
set to
Select the lowest-numbered
message buffer.
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