Message Reception - NEC V850ES/F 3-L Series User Manual

Chapter 18

18.9 Message Reception

18.9.1 Message reception
Table 18-24
602
In all the operation modes, the complete message buffer area is analyzed to
find a suitable buffer to store a newly received message. All message buffers
satisfying the following conditions are included in that evaluation (RX-search
process).
• Used as a message buffer
(MA0 bit of CnMCONFm register set to 1.)
• Set as a receive message buffer
(MT[2:0] bits of CnMCONFm register are set to 001
101 .)
B
• Ready for reception
(RDY bit of CnMCTRLm register is set to 1.)
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 message is not stored in the message buffer linked to mask 1,
even if that message buffer has not received a message and a message has
already been received in the unmasked receive message buffer. In other
words, when a condition has been set 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 message buffers with a lower
priority. This also applies when the message buffer with the highest priority is
unable to store a message (i.e., when DN = 1 indicating that a message has
already been received, but rewriting is disabled because OWS = 0). In this
case, the message is not actually stored in the candidate message buffer with
the highest priority, but neither is it stored in a message buffer with a lower
priority.
MBRB priorities
Priority Storing condition if same ID is set
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
User's Manual U18743EE1V2UM00
CAN Controller (CAN)
, 010 , 011 , 100
B B B B
DN bit = 0
DN bit = 1 and OWS bit = 1
DN bit = 0
DN bit = 1 and OWS bit = 1
DN bit = 0
DN bit = 1 and OWS bit = 1
DN bit = 0
DN bit = 1 and OWS bit = 1
DN bit = 0
DN bit = 1 and OWS bit = 1
, or