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Section 20 Controller Area Network
R01UH0134EJ0400 Rev. 4.00 Page 997 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
DLC[3:0] (Data Length Code): These bits encode the number of data bytes from 0,1, 2, … 8 that
will be transmitted in a data frame. Please note that when a remote frame request is transmitted the
DLC value to be used must be the same as the DLC of the data frame that is requested.
DLC[3] DLC[2] DLC[1] DLC[0] Description
0 0 0 0 Data Length = 0 bytes (Initial value)
0 0 0 1 Data Length = 1 byte
0 0 1 0 Data Length = 2 bytes
0 0 1 1 Data Length = 3 bytes
0 1 0 0 Data Length = 4 bytes
0 1 0 1 Data Length = 5 bytes
0 1 1 0 Data Length = 6 bytes
0 1 1 1 Data Length = 7 bytes
1 x x x Data Length = 8 bytes
(2) Local Acceptance Filter Mask (LAFM)
This area is used as Local Acceptance Filter Mask (LAFM) for receive boxes.
LAFM: When MBC is set to 001, 010, 011(Bin), this field is used as LAFM Field. It allows a
Mailbox to accept more than one identifier. The LAFM is comprised of two 16-bit read/write
areas as follows.
Word/LW
Word
H'104 + N
*
32
H'106 + N
*
32
LAFM Field
1514131211109876543210
EXTID_
LAFM[17:16]
IDE_
LAFM
0 0
STDID_LAFM[10:0]
EXTID_LAFM[15:0]
Figure 20.4 Acceptance filter
If a bit is set in the LAFM, then the corresponding bit of a received CAN identifier is ignored
when this module searches a Mailbox with the matching CAN identifier. If the bit is cleared, then
the corresponding bit of a received CAN identifier must match to the STDID/IDE/EXTID set in
the mailbox to be stored. The structure of the LAFM is same as the message control in a Mailbox.
If this function is not required, it must be filled with '0'.
Important: This module starts to find a matching identifier from Mailbox-31 down to Mailbox-0.
As soon as this module finds one matching, it stops the search. The message will be stored or not
depending on the NMC and RXPR/RFPR flags. This means that, even using LAFM, a received
message can only be stored into 1 Mailbox.