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D
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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
335 of 571
NXP Semiconductors
UM10316
Chapter 21: LPC29xx CAN 0/1
9.14 CAN controller transmit-buffer identifier registers
The CAN controller transmit buffer identifier registers CCTXB1ID, CCTXB2ID and
CCTXB3ID contain the identifier field of the transmit message. These registers are only
writable when the transmit buffer is released (i.e corresponding transmit-buffer status bit is
logic 1).
shows the bit assignment of the CCTXB1ID, CCTXB2ID and CCTXB3ID
registers.
9.15 CAN controller transmit-buffer data A registers
The CAN controller transmit-buffer data A registers CCTXB1DA, CCTXB2DA and
CCTXB3DA contain the first four data bytes of the transmit message. These registers are
only writable when the transmit buffer is released (i.e. corresponding transmit-buffer
status bit is logic 1).
19 to 16 DLC[3:0]
R/W
0h
Data-length code. This register contains the
number of data bytes to be transmitted if bit
RTR is logic 0, or the requested number of data
bytes if bit RTR is logic 1. Values greater than
eight are handled as eight data bytes
0h*
15 to 8
reserved
R
-
Reserved; do not modify. Read as logic 0
7 to 0
TXPRIO[7:0]
R/W
Transmit priority. If the transmit-priority mode bit
in the CAN controller mode register is set, the
transmit buffer with the lowest transmit-priority
value wins the prioritization and is sent first. In
cases where the same transmit priority or the
same ID is chosen for more than one transmit
buffer, the transmit buffer with the lowest buffer
number is sent first
00h*
Table 280. CAN controller transmit-buffer message info register bit description
(CCTXB1/2/3MI, addresses 0xE008 0030, 0xE008 0040, 0xE008 0050 (CAN0), and
0xE008 1030, 0xE008 1040, 0xE008 1050 (CAN1))
…continued
* = reset value
Bit
Symbol
Access
Value
Description
Table 281. CAN controller transmit-buffer identifier register bit description (CCTXB1/2/3ID,
addresses 0xE008 0034, 0xE008 0044, 0xE008 0054 (CAN0), and 0xE008 1034,
0xE008 1044, 0xE008 1054 (CAN1))
* = reset value
Bit
Symbol
Access
Value
Description
31 to 29 reserved
R
-
Reserved; do not modify. Read as logic 0
28 to 0
ID[28:0]
R/W
Identifier register. This contains the
identifier of the transmit CAN message. If
a standard frame-format is transmitted the
11 least significant bits must represent the
11-bit identifier
0000 0000h*