816
Chapter 18
AFCAN Controller
User’s Manual U16580EE3V1UD00
18.10 Message
Transmission
18.10.1 Message
transmission
A message buffer with its TRQ bit set to 1 participates in the search for the most high-prioritized mes-
sage when the following conditions are fulfilled. This behavior is valid for all operational modes.
•
Used as a message buffer
(MA0 bit of CnMCONFm register set to 1B.)
•
Set as a transmit message buffer
(MT[2:0] bits of CnMCONFm register set to 000B.)
•
Ready for transmission
(RDY bit of CnMCTRLm register set to 1.)
The CAN system is a multi-master communication system. In a system like this, the priority of message
transmission is determined based on message identifiers (IDs). To facilitate transmission processing by
software when there are several messages awaiting transmission, the CAN module uses hardware to
check the ID of the message with the highest priority and automatically identifies that message. This
eliminates the need for software-based priority control.
Transmission priority is controlled by the identifier (ID).
Figure 18-30:
Message processing example
After the transmit message search, the transmit message with the highest priority of the transmit mes-
sage buffers that have a pending transmission request (message buffers with the TRQ bit set to 1 in
advance) is transmitted.
If a new transmission request is set, the transmit message buffer with the new transmission request is
compared with the transmit message buffer with a pending transmission request. If the new transmis-
sion request has a higher priority, it is transmitted, unless transmission of a message with a low priority
has already started. If transmission of a message with a low priority has already started, however, the
new transmission request is transmitted later. To solve this priority inversion effect, the software can
perform a transmission abort request for the lower priority message. The highest priority is determined
according to the following rules.
Message No.
The CAN module transmits messages in the following sequence.
Message waiting to be transmitted
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
Summary of Contents for MuPD70F3187
Page 6: ...6 Preface User s Manual U16580EE3V1UD00 ...
Page 16: ...16 User s Manual U16580EE3V1UD00 ...
Page 28: ...28 User s Manual U16580EE3V1UD00 ...
Page 32: ...32 User s Manual U16580EE3V1UD00 ...
Page 84: ...84 Chapter 2 Pin Functions User s Manual U16580EE3V1UD00 MEMO ...
Page 144: ...144 Chapter 3 CPU Functions User s Manual U16580EE3V1UD00 MEMO ...
Page 312: ...312 Chapter 9 16 Bit Timer Event Counter P User s Manual U16580EE3V1UD00 MEMO ...
Page 534: ...534 Chapter 11 16 bit Timer Event Counter T User s Manual U16580EE3V1UD00 ...
Page 969: ...969 Chapter 20 Port Functions User s Manual U16580EE3V1UD00 MEMO ...
Page 970: ...970 Chapter 20 Port Functions User s Manual U16580EE3V1UD00 ...
Page 976: ...976 Chapter 22 Internal RAM Parity Check Function User s Manual U16580EE3V1UD00 MEMO ...
Page 984: ...984 Chapter 23 On Chip Debug Function OCD User s Manual U16580EE3V1UD00 MEMO ...
Page 1006: ...1006 Chapter 24 Flash Memory User s Manual U16580EE3V1UD00 MEMO ...
Page 1036: ...1036 Chapter 27 Recommended Soldering Conditions User s Manual U16580EE3V1UD00 MEMO ...
Page 1046: ...1046 Appendix A Index User s Manual U16580EE3V1UD00 MEMO ...
Page 1052: ...1052 User s Manual U16580EE3V1UD00 ...
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