Message RAM
1542
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Controller Area Network (CAN)
Table 23-2. Message Object Field Descriptions (continued)
Name
Value
Description
Data 0
1st data byte of a CAN data frame
Data 1
2nd data byte of a CAN data frame
Data 2
3rd data byte of a CAN data frame
Data 3
4th data byte of a CAN data frame
Data 4
5th data byte of a CAN data frame
Data 5
6th data byte of a CAN data frame
Data 6
7th data byte of a CAN data frame
Data 7
8th data byte of a CAN data frame
Note: Byte Data 0 is the first data byte shifted into the shift register of the CAN Core during a reception,
byte Data 7 is the last. When the message handler stores a data frame, it will write all the eight data bytes
into a message object. If the data length code is less than 8, the remaining bytes of the message object
may be overwritten by undefined values.
23.14.2 Addressing Message Objects in RAM
The starting location of a particular message object in RAM is:
Message RAM base a (message object number) * 0x20.
This means that Message Object 1 starts at offset 0x0020; Message Object 2 starts at offset 0x0040, etc.
NOTE:
'0' is not a valid message object number. At address 0x0000, the last message object (32)
(with the lowest priority) is located. Writing to the address of an unimplemented message
object may overwrite an implemented message object.
Message Object number 1 has the highest priority.
(1)
See
Table 23-3. Message RAM Addressing in Debug Mode
Message Object Number
Offset From Base
Address
Word Number
Debug Mode
(1)
last implemented (here:32)
0x0000
1
Parity
0x0004
2
MXtd,MDir,Mask
0x0008
3
Xtd,Dir,ID
0x000C
4
Ctrl
0x0010
5
Data Bytes 3-0
0x0014
6
Data Bytes 7-4
1
0x0020
1
Parity
0x0024
2
MXtd,MDir,Mask
0x0028
3
Xtd,Dir,ID
0x002C
4
Ctrl
0x0030
5
Data Bytes 3-0
0x0034
6
Data Bytes 7-4
2
0x0040
1
Parity
0x0044
2
MXtd,MDir,Mask
0x0048
3
Xtd,Dir,ID
0x004C
4
Ctrl
0x0050
5
Data Bytes 3-0
0x0054
6
Data Bytes 7-4
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