Table 14-14: Inner Storage Priority Within A Priority Class - NEC V850E/CA2 JUPITER Preliminary User's Manual

Table 14-14: Inner Storage Priority Within a Priority Class

Priority First Criteria
1 (high) DN flag not set
2 (low) DN flag set
Example:
When the very first message is received, which fits into several message buffer of the same prior-
ity class, the DN flag in all buffers is not set, hence that message is stored in the buffer with the
lowest physical buffer number. Subsequent messages are stored to the message buffers in
ascending message buffer number order as long the DN flags remains as set into the buffer of the
previous message storage.
As soon the CPU reads one of the message buffer with DN flag set and then clears the DN flag,
the storing in ascending message buffer number order is interrupted.
Due to the storage priority for receive messages it is possible to design multiple buffer arrays for a
CAN message – while not all message buffers assigned to the same identifier contain new data
(DN flag set) the FCAN system will store the data in the next free message buffer (DN flag
cleared).
Preliminary User's Manual U15839EE1V0UM00
Chapter 14 FCAN Interface Function
Priority
1 (high)
2 (low)
1 (high)
2 (low)
Second Criteria
lowest physical message buffer number
next physical message buffer number
lowest physical message buffer number
next physical message buffer number
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