BAT32G1x9 user manual | Chapter 22 CAN control
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Rev.1.02
Priority
condition
description
1 (high).
The value of the first 11 bits of
the ID [ID18
to
ID28]:
The message frame of the lowest value represented by the first
11 bits of the ID is sent first. If the value of the 11-bit standard ID
is equal to or less than the first 11 bits of the 29-bit extension ID,
the priority of the 11-bit standard ID is higher than that of the
packet frame with the 29-bit extension ID.
2
The frame type
Data frames with an 11-bit standard ID (RTR bit cleared to 0)
have a higher priority than remote frames with standard IDs and
packet frames with extended IDs.
3
The ID type
Packet frames with a standard ID (ID bit cleared to 0) have a
higher priority than packet frames with extended IDs
4
The value of the ID low 18
bits [ID0
to
ID17]:
If multiple packet frames that send pending extension ID have the
same value and the same frame type (equal to the RTR bit value)
in the first 11 bits of the ID, the message frame with the lowest
median value of their extended ID low 18 bits is transmitted first
5 (low).
Message cache number
If two or more packet buffers request to send a message frame
with the same ID, the message from the message buffer with the
lowest message buffer number is transmitted first.
Note 1 If the auto block transfer request bit ABTTRG is set to 1 in normal operating mode with ABT, the TRQ
bit of only one packet cache in the ABT packet cache group is set to 1. If the ABT pattern is triggered
by the ABTTRG bit, one of the TRQ bits in the ABT region is set to 1 (buffers 0 to 7). In addition to this
TRQ bit, the application can request other TX packet buffer transfers that are not part of the ABT
region (set the TRQ to 1). In this case, the Interval Arbitration Process (TX-search) evaluates all TX
packet buffers with the TRQ bit set to 1 and selects the packet buffer with the highest priority identifier
for the next transmission. If 2 or more identifiers have the highest priority (i.e. the same identifier), the
message at the lowest packet buffer number is transmitted first.
After the message frame is successfully transmitted, the following actions are performed:
- The TRQ flag for the corresponding transmit packet buffer is automatically cleared to 0.
- The transmit completion status bit CINTS0 of the CnINTS register is set to 1 (if the interrupt enable bit (IE) of
the corresponding transmit packet buffer is set to 1).
- Interrupt request signal INCNTRX output (if the CIE0 bit of the CnIE register is set to 1 and the interrupt
enable bit (IE) of the corresponding transmit packet buffer is set to 1.
2.
When changing the contents of a send buffer, you must clear the RDY flag for this buffer before updating the
contents of the buffer. As with internal transfer operations, the RDY flag may be temporarily locked, and the
status of the RDY must be checked by the software after the change.
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