CHAPTER 11 FCAN CONTROLLER
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User’s Manual U14492EJ3V0UD
11.5 Message Processing
A modular system is used for the FCAN controller. Consequently, messages can be placed at any location within
the message area.
The messages can be linked to mask functions that are in turn linked to CAN modules.
The FCAN system is a multiplexed communication system. The priority of message transmission within this
system is determined based on message identifiers (IDs).
To facilitate transmission processing by application software when there are several messages awaiting
transmission, the CAN module uses hardware to check the message IDs and automatically determine whether or not
linked messages are prioritized.
This eliminates the need for software-based priority control.
Figure 11-5. Example of Message Processing
Message number
CAN module transmits messages in the following order.
Messages awaiting transmission
ID = 120H
ID = 229H
ID = 223H
ID = 023H
ID = 123H
0
1
2
3
4
5
6
7
8
9
1. Message 6
2. Message 1
3. Message 8
4. Message 5
5. Message 2
This auto priority control function can be canceled. When it is canceled, the priority among messages is
determined based on the locations of the messages in memory (the message that has the lowest message number
among the messages in the message buffer has the highest priority).
When several messages have been received in the CAN module’s message buffers, priority control for storing
received messages is as follows.
Priority rank 1: Remote frame reception in the transmit message buffer.
Priority rank 2: Non-masked message, for which M_STATn register’s DN bit has not been set (to 1)
Priority rank 3: Non-masked message, for which M_STATn register’s DN bit has been set (to 1)
Priority rank 4: Mask 0 message, for which M_STATn register’s DN bit has not been set (to 1)
Priority rank 5: Mask 0 message, for which M_STATn register’s DN bit has been set (to 1)
Priority rank 6: Mask 1 message, for which M_STATn register’s DN bit has not been set (to 1)
Priority rank 7: Mask 1 message, for which M_STATn register’s DN bit has been set (to 1)
Priority rank 8: Mask 2 message, for which M_STATn register’s DN bit has not been set (to 1)
Priority rank 9: Mask 2 message, for which M_STATn register’s DN bit has been set (to 1)
Priority rank 10: Mask 3 message, for which M_STATn register’s DN bit has not been set (to 1)
Priority rank 11: Mask 3 message, for which M_STATn register’s DN bit has been set (to 1)
Remark
n = 00 to 31
Содержание V850E/IA1 mPD703116
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