Fujitsu MB90390 Series Hardware Manual page 525

When using the message buffer (x) in the standard frame format (IDEx of the IDE register (IDER) = 0), use
11 bits of ID28 to ID18. When using the buffer in the extended frame format (IDEx = 1), use 29 bits of
ID28 to ID0.
ID28 to ID0 have the following functions:
• Set acceptance code (ID for comparing with the received message ID).
• Set transmitted message ID.
Note:
In the standard frame format, setting 1s to all bits of ID28 to ID22 is prohibited.
• Store the received message ID.
Notes:
• All received message ID bits are stored (even if bits are masked). In the standard frame format,
ID17 to ID0 stores image of old message left in the receive shift register.
• A write operation to this register should be performed in words. A write operation in bytes causes
undefined data to be written to the upper byte at writing to the lower byte. Writing to the upper
byte is ignored.
This register should be set when the message buffer (x) is invalid (BVALx of the message buffer
valid register (BVALR) is "0"). Setting when the buffer is valid (BVALx = 1) may cause
unnecessary received messages to be stored.
To invalidate the message buffer (by setting the BVALR: BVAL bit to "0") while the CAN controller
is operating for CAN communication (the read value of the CSR: HALT bit is "0" and the CAN
controller is operating for CAN bus communication to enable transmission and reception), follow
the procedure in Section "23.16 Precautions when Using CAN Controller".
CHAPTER 23 CAN CONTROLLER
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