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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
314 of 571
NXP Semiconductors
UM10316
Chapter 21: LPC29xx CAN 0/1
Each CAN identifier is linked to an ID Index number (see also
and
). For a CAN identifier match, the matching ID index is stored in the identifier
index IDI of the message info register CCRXBMI for the appropriate CAN controller (see
for more details).
8.10 CAN acceptance-filter search algorithm
The identifier-screening process of the acceptance filter starts in the following order:
1. FullCAN (standard frame-format) identifier section
2. Explicit standard frame-format identifier section
3. Group of standard frame-format identifier section
4. Explicit extended frame-format identifier section
5. Group of extended frame-format identifier section
Remark:
Only activated sections take part in the screening process.
In cases where equal message identifiers of the same frame format are defined in more
than one section, the first match ends the screening process for this identifier. For
example, if the same source CAN channel in conjunction with the identifier is defined in
the FullCAN, explicit standard frame-format and group of standard frame-format identifier
sections, screening will finish with the match in the FullCAN section.
, identifiers with their SCC have been defined in the FullCAN, explicit and
group of standard frame-format identifier sections. The identifier 5Ah of Source CAN
Channel 0 is defined in all three sections. With this configuration, incoming CAN
messages on Source CAN Channel 0 with a 5Ah identifier find a match in the FullCAN
section.
Fig 76. ID look-up table example explaining the search algorithm
0
FullCAN
Explicit
Standard
Frame
Format
Identifier
Section
Explicit
Standard
Frame
Format
Identifier
Section
Group of
Standard
Frame
Format
Identifier
Section
ID = 5Ah
...
...
...
...
...
...
ID = 5Ah
ID = 0x5A
...
SCC = 0
SCC = 2
SCC = 4
SCC = 5
SCC = 0
SCC = 2
SCC = 4
SCC = 0
SCC = 1
SCC = 0
SCC = 1
SCC = 5
SCC = 0
SCC = 1
SCC = 3
SCC = 0
SCC = 1
...
SCC = 3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Message
disable bit
ID = 5Ah
...
...
...
...
...
ID = 5Fh
...
Message
disable bit
Index 0, 1
Index 2, 3
Index 4, 5
Index 6, 7
Index 8, 9
Index 10, 11
Index 12, 13
Index 14
Index 15