Message Reception - NEC V850E/RS1 User Manual

16.9 Message Reception

16.9.1 Message reception
In all the operation modes, when a message is received, a message buffer that is to store the message
is searched from all the message buffers satisfying the following conditions.
• Used as a message buffer
• Set as a receive message buffer
• Ready for reception
When two or more message buffers of the CAN module receive a message, the message is stored
according to the priority explained below. The message is always stored in the message buffer with the
highest priority, not in a message buffer with a low priority. For example, when an unmasked receive
message buffer and a receive message buffer linked to mask 1 have the same ID, the received mes-
sage is not stored in the message buffer linked to mask 1 that has not received a message, even if a
message has already been received in the unmasked receive message buffer. In other words, when a
condition has been set to store a message in two or more message buffers with different priorities, the
message buffer with the highest priority always stores the message; the message is not stored in mes-
sage buffers with a lower priority. This also applies when the message buffer with the highest priority is
unable to receive and store a message (i.e., when the DN bit = 1 indicating that a message has already
been received, but rewriting is disabled because the OWS bit = 0). In this case, the message is not
actually received and stored in the candidate message buffer with the highest priority, but neither is it
stored in a message buffer with a lower priority.
Remark:
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Chapter 16 FCAN Controller
(MA0 bit of CnMCONFm register set to 1B.)
(MT[2:0] bits of CnMCONFm register set to 001B, 010B, 011B, 100B, or 101B.)
(RDY bit of CnMCTRLm register set to 1.)
Priority
1 (high) Unmasked message buffer
2 Message buffer linked to mask 1
3 Message buffer linked to mask 2
4 Message buffer linked to mask 3
5 (low) Message buffer linked to mask 4
n = 0, 1
m = 0-31
User's Manual U16702EE3V2UD00
Storing Condition If Same ID Is Set
DN = 1 and OWS = 1
DN = 1 and OWS = 1
DN = 1 and OWS = 1
DN = 1 and OWS = 1
DN = 1 and OWS = 1
DN = 0
DN = 0
DN = 0
DN = 0
DN = 0
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