NXP Semiconductors LPC24XX UM10237 - Manual (Page 507)

UM10237_4 © NXP B.V. 2009. All rights reserved.
User manual Rev. 04 — 26 August 2009 507 of 792
NXP Semiconductors
UM10237
Chapter 18: LPC24XX CAN controllers CAN1/2
The identifier 0x5A of the CAN Controller 1 with the Source CAN Channel SCC = 1, is
defined in all three sections. With this configuration incoming CAN messages on CAN
Controller 1 with a 0x5A identifier will find a match in the FullCAN section.
It is possible to disable the ‘0x5A identifier’ in the FullCAN section. With that, the
screening process would be finished with the match in the Explicit Identifier Section.
The first group in the Group Identifier Section has been defined in that way, that incoming
CAN messages with identifiers of 0x5A up to 0x5F are accepted on CAN Controller 1 with
the Source CAN Channel SCC = 1. As stated above, the identifier 0x5A would find a
match already in the FullCAN or in the Explicit Identifier section if enabled. The rest of the
defined identifiers of this group (0x5B to 0x5F) will find a match in this Group Identifier
Section.
This way the user can switch dynamically between different filter modes for same
identifiers.
17. FullCAN mode
The FullCAN mode is based on capabilities provided by the CAN Gateway module used in
the LPC2000 family of products. This block uses the Acceptance Filter to provide filtering
for both CAN channels.
The concept of the CAN Gateway block is mainly based on a BasicCAN functionality. This
concept fits perfectly in systems where a gateway is used to transfer messages or
message data between different CAN channels. A BasicCAN device is generating a
Fig 81. ID Look-up table example explaining the search algorithm
SCC = 1
SCC = 2
SCC = 1
SCC = 2
SCC = 1
SCC = 3
SCC = 5
SCC = 1
SCC = 2
SCC = 4
0 FullCAN
Explicit
Standard
Frame
Format
Identifier
Section
Explicit
Standard
Frame
Format
Identifier
Section
Group of
Standard
Frame
Format
Identifier
Section
ID = 0x5A ...
... ...
...
... ...
ID = 0x5A ID = 0x5A
...
SCC = 1
SCC = 3
SCC = 5
SCC = 6
SCC = 1
SCC = 2
SCC = 6
... SCC = 4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Message
disable bit
ID = 0x5A
...
...
...
...
...
ID = 0x5F
...
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