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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
340 of 808
NXP Semiconductors
UM10360
Chapter 16: LPC17xx CAN1/2
7.9.1 ID index field
The ID Index is a 10-bit field in the Info Register that contains the table position of the ID
Look-up Table if the currently received message was accepted. The software can use this
index to simplify message transfers from the Receive Buffer into the Shared Message
Memory. Whenever bit 10 (BP) of the ID Index in the CANRFS register is 1, the current
CAN message was received in acceptance filter bypass mode.
7.10 CAN Receive Identifier register (CAN1RID - 0x4004 4024, CAN2RID -
0x4004 8024)
This register contains the Identifier field of the current received message. It is read-only in
normal operation but can be written for testing purposes if the RM bit in CANmod is 1. It
has two different formats depending on the FF bit in CANRFS. See
details on specific CAN channel register address.
7.11 CAN Receive Data register A (CAN1RDA - 0x4004 4028, CAN2RDA -
0x4004 8028)
This register contains the first 1-4 Data bytes of the current received message. It is
read-only in normal operation, but can be written for testing purposes if the RM bit in
CANMOD is 1. See
for details on specific CAN channel register address.
Table 306. CAN Receive Identifier register (CAN1RID - address 0x4004 4024, CAN2RID -
address 0x4004 8024) bit description
Bit
Symbol Function
Reset Value RM Set
10:0
ID
The 11-bit Identifier field of the current received
message. In CAN 2.0A, these bits are called ID10-0,
while in CAN 2.0B they’re called ID29-18.
0
X
31:11 -
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
NA
Table 307. RX Identifier register when FF = 1
Bit
Symbol Function
Reset Value RM Set
28:0
ID
The 29-bit Identifier field of the current received
message. In CAN 2.0B these bits are called ID29-0.
0
X
31:29 -
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
NA
Table 308. CAN Receive Data register A (CAN1RDA - address 0x4004 4028, CAN2RDA -
address 0x4004 8028) bit description
Bit
Symbol Function
Reset
Value
RM
Set
7:0
Data 1
If the DLC field in CANRFS
≥
0001, this contains the first Data byte
of the current received message.
0
X