NXP Semiconductors LPC24XX UM10237 - Manual (Page 490)

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User manual Rev. 04 — 26 August 2009 490 of 792
NXP Semiconductors
UM10237
Chapter 18: LPC24XX CAN controllers CAN1/2
8.9.1 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.
8.10 Receive Identifier Register (CAN1RID - 0xE004 4024, CAN2RID -
0xE004 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
Table 18–417 for
details on specific CAN channel register address.
8.11 Receive Data Register A (CAN1RDA - 0xE004 4028, CAN2RDA -
0xE004 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
Table 18–417 for details on specific CAN channel register address.
Table 429. Receive Identifier Register (CAN1RID - address 0xE004 4024, CAN2RID - address
0xE004 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 430. 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 431. Receive Data register A (CAN1RDA - address 0xE004 4028, CAN2RDA - address
0xE004 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