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R01UH0336EJ0102 Rev.1.02
Page 1103 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 20 CAN Controller (FCN)
20.7.2
Receive Data Read
To keep data consistency when reading message buffers, read data according
to the procedures in Figure 20-31, Reception via Interrupt (Using
FCNnCMLISTR Register), to Figure 20-34, Reception via Software Polling.
During message reception, the FCN module sets
FCNnMmCTL.FCNnMmDTNF two times: at the beginning of the storage
process of data to the message buffer, and again at the end of this storage
process. During this storage process, FCNnMmCTL.FCNnMmMUCF of the
message buffer is set (see Figure 20-6, Reception Timing).
The receive history list is also updated just before the storage process. In
addition, during storage process (FCNnMmCTL.FCNnMmMUCF = 1),
FCNnMmCTL.FCNnMmRDYF of the message buffer is locked to avoid any
coincidental data write by the CPU. Note that the storage process may be
disturbed (delayed) when the CPU accesses the message buffer.
Caution
To securely store a message in the message buffer, the
FCNnMmCTL.FCNnMmDTNF bit of the buffer must be cleared before the
message search processing is started (before the frame ID is output to the
bus). This is the 15th of CAN bits after EOF of the previous frame at shortest.
To securely receive CAN frames that continuously appear on the bus, it is
recommended that one more message buffers for frame reception be used.
Figure 20-6
Reception Timing
SOF
(1)
ID
IDE
RTR
R0
DLC
DATA0-DATA7
CRC
ACK EOF
CAN standard
ID format
(11)
(1)
(1)
(1)
(4)
(0-64)
(16)
(2)
Recessive
Dominant
FCNnMmDTNF
FCNnMmMUCF
Message store
MDATA,MDLC.MIDx -> MBUF
Message search
(The DN bit in the target receive buffer must be cleared to 0)
(7)
FCNnCMISITSF1
FCNnMmDTNF and
FCNnMmMUCF
at the same time
Set FCNnMmDTNF and
clear FCNnMmMUCF
at the same time
IFS
INTFCNnREC1
Operation of the CAN contoroller
Extension of timing for IFS
30/f
CAN
1/f
CAN
RHL and LISSLR
are updated
1/f
CAN
2/f
CAN
1/f
CAN
-3/f
CAN