CAN Control Registers
1561
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Controller Area Network (CAN)
Table 23-21. IF1 and IF2 Message Control Registers Field Descriptions (continued)
Bit
Field
Value
Description
8
TxRqst
Transmit Request
0
This message object is not waiting for a transmission.
1
The transmission of this message object is requested and is not yet done.
7
EoB
End of Block
0
The message object is part of a FIFO Buffer block and is not the last message object of the FIFO
Buffer block.
1
The message object is a single message object or the last message object in a FIFO Buffer Block.
Note: This bit is used to concatenate multiple message objects to build a FIFO Buffer. For single
message objects (not belonging to a FIFO Buffer), this bit must always be set to one.
6-5
Reserved
Reserved
3-0
DLC[3:0]
Data length code
0-8
Data frame has 0-8 data bits.
9-15
data frame has 8 data bytes.
Note: The data length code of a message object must be defined the same as in all the
corresponding objects with the same identifier at other nodes. When the message handler stores a
data frame, it will write the DLC to the value given by the received message.
23.15.18
IF1 and IF2 Data A and Data B Registers (CAN IF1DATA/DATB, CAN IF2DATA/DATB)
The data bytes of CAN messages are stored in the IF1 and IF2 registers in the following order. In a CAN
data frame, Data 0 is the first, and Data 7 is the last byte to be transmitted or received. In CAN's serial bit
stream, the MSB of each byte will be transmitted first
Figure 23-40. IF1 Data A Register (CAN IF1DATA) [offset = 0x110]
31
24
23
16
Data 3
Data 2
R/WP-0
R/WP-0
15
8
7
0
Data 1
Data 0
R/WP-0
R/WP-0
LEGEND: R = Read; WP = Protected Write (protected by Busy bit); -
n
= value after reset
Figure 23-41. IF1 Data B Register (CAN IF1DATB) [offset = 0x114]
31
24
23
16
Data 7
Data 6
R/WP-0
R/WP-0
15
8
7
0
Data 5
Data 4
R/WP-0
R/WP-0
LEGEND: R = Read; WP = Protected Write (protected by Busy bit); -
n
= value after reset
Figure 23-42. IF2 Data A Register (CAN IF2DATA) [offset = 0x130]
31
24
23
16
Data 3
Data 2
R/WP-0
R/WP-0
15
8
7
0
Data 1
Data 0
R/WP-0
R/WP-0
LEGEND: R = Read; WP = Protected Write (protected by Busy bit); -
n
= value after reset