UM10562 Datasheet, PDF (562/942 Pages) NXP Semiconductors – LPC408x/407x User manual

NXP Semiconductors
UM10562
Chapter 20: LPC408x/407x CAN controller
Table 448. CAN Receive Data register A (CAN1RDA - address 0x4004 4028, CAN2RDA - address 0x4004 8028) bit
description
Bit Symbol Function
Reset Value RM Set
7:0 DATA1 Data 1. If the DLC field in CANRFS  0001, this contains the first Data byte of the
0
X
current received message.
15:8 DATA2 Data 2. If the DLC field in CANRFS  0010, this contains the first Data byte of the
0
X
current received message.
23:16 DATA3 Data 3. If the DLC field in CANRFS  0011, this contains the first Data byte of the
0
X
current received message.
31:24 DATA4 Data 4. If the DLC field in CANRFS  0100, this contains the first Data byte of the
0
X
current received message.
20.7.12 CAN Receive Data register B
This register contains the 5th through 8th 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.
Table 449. CAN Receive Data register B (CAN1RDB - address 0x4004 402C, CAN2RDB - address 0x4004 802C) bit
description
Bit Symbol Function
Reset Value RM Set
7:0 DATA5 Data 5. If the DLC field in CANRFS  0101, this contains the first Data byte of the
0
X
current received message.
15:8 DATA6 Data 6. If the DLC field in CANRFS  0110, this contains the first Data byte of the
0
X
current received message.
23:16 DATA7 Data 7. If the DLC field in CANRFS  0111, this contains the first Data byte of the
0
X
current received message.
31:24 DATA8 Data 8. If the DLC field in CANRFS  1000, this contains the first Data byte of the
0
X
current received message.
20.7.13 CAN Transmit Frame Information register
When the corresponding TBS bit in CANSR is 1, software can write to one of these
registers to define the format of the next transmit message for that Tx buffer. Bits not listed
read as 0 and should be written as 0.
The values for the reserved bits of the CANxTFI register in the Transmit Buffer should be
set to the values expected in the Receive Buffer for an easy comparison, when using the
Self Reception facility (self test), otherwise they are not defined.
The CAN Controller consist of three Transmit Buffers. Each of them has a length of 4
words and is able to store one complete CAN message as shown in Figure 80.
The buffer layout is subdivided into Descriptor and Data Field where the first word of the
Descriptor Field includes the TX Frame Info that describes the Frame Format, the Data
Length and whether it is a Remote or Data Frame. In addition, a TX Priority register allows
the definition of a certain priority for each transmit message. Depending on the chosen
Frame Format, an 11-bit identifier for Standard Frame Format (SFF) or an 29-bit identifier
for Extended Frame Format (EFF) follows. Note that unused bits in the TID field have to
be defined as 0. The Data Field in TDA and TDB contains up to eight data bytes.
UM10562
User manual
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 13 September 2012
© NXP B.V. 2012. All rights reserved.
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