Fujitsu FR81S Manuale Utente
CHAPTER 41: CAN
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER
: CAN
FUJITSU SEMICONDUCTOR CONFIDENTIAL
65
5.2.2. Transmission Priority
Transmission priority is shown.
Transmission priority of a message object is determined by its message number. Message object 1 has the
highest priority; and message object 32 (or the maximum equipped message object number) has the lowest
priority. Therefore, if 2 or more transmission requests are pending, message objects will be transferred in
the order starting from the message object having the smallest corresponding message number.
Notes:
⋅
When the message buffer with the lowest priority is used for transmission and the TXRqst is set to "1"
and then to "0" to cancel transmission, setting the TXRqst to "1" again may not, depending on the timing,
result in transmission of a message until one of the following events occurs:
⋅
A valid message is transmitted on the CAN bus.
⋅
A transmission request is issued to other message buffer.
⋅
CAN is initialized by the Init bit.
If there is a situation in which transmission is canceled due to system reasons, either do not use the
message buffer with the lowest priority as the transmission message buffer or, after transmission
cancellation, generate one of the above events and then set the TxRqst to "1" again.
⋅
When the TxRqst bit is "1", do not change the message objects of ID28 to ID0, DLC3 to DLC0, Xtd, and
Data7 to Data0. Otherwise, message objects before and after the change may be transmitted in a mixed
way or message objects after the change may not be transmitted. Change them when the TxRqst bit is "0".
MB91520 Series
MN705-00010-1v0-E
1758