Transmit Buffer; Table 22-27. Can Transmit Buffer - Sharp Blue Treak LH75400 User Manual

LH75400/01/10/11 (Preliminary) User's Guide

22.3.2.13 Transmit Buffer

The CAN Transmit Buffer has a length of 13 bytes. It accommodates one Transmit
message of up to eight data bytes.
Write Only access to the Transmit Buffer is provided in Operating Mode using CAN
offsets 0x40 - 0x70.
Table 22-27 shows the global layout of the Transmit Buffer. It is essential to distinguish
between SFF and EFF messages.
The CAN transmit buffer is divided into descriptor and data fields. The first byte of the
descriptor field holds frame information. It describes the frame format (SFF or EFF), remote
or data frame, and data length. This is then followed by either two identifier bytes for SFF
messages or four bytes for EFF messages. The data field contains up to eight data bytes.
NOTE: Direct read-only access to the Transmit Buffer is possible using the CAN offset space from
0x180 to 0x1B0.

Table 22-27. CAN Transmit Buffer

STANDARD FRAME FORMAT
CAN OFFSET
0x40 TX Frame Information
0x44 TX Identifier 1
0x48 TX Identifier 2
0x4C TX Data Byte 1
0x50 TX Data Byte 2
0x54 TX Data Byte 3
0x58 TX Data Byte 4
0x5C TX Data Byte 5
0x60 TX Data Byte 6
0x64 TX Data Byte 7
0x68 TX Data Byte 8
0x6C
0x70
EXTENDED FRAME FORMAT
FIELD CAN OFFSET
0x40
0x44
0x48
0x4C
0x50
0x54
0x58
0x5C
0x60
0x64
0x68
(Unused) 0x6C
(Unused) 0x70
6/17/03
Controller Area Network
FIELD
TX Frame Information
TX Identifier 1
TX Identifier 2
TX Identifier 3
TX Identifier 4
TX Data Byte 1
TX Data Byte 2
TX Data Byte 3
TX Data Byte 4
TX Data Byte 5
TX Data Byte 6
TX Data Byte 7
TX Data Byte 8
22-23