DCAN Control Registers
1480
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Controller Area Network (DCAN) Module
Table 27-25. IF1/IF2 Command Register Field Descriptions (continued)
Bit
Field
Value
Description
16
Data B
Access Data Bytes 4–7.
0
Data Bytes 4–7 will not be changed.
1
Direction = Read: The Data Bytes 4–7 will be transferred from the message object addressed
by the Message Number (Bits [7:0]) to the corresponding IF1/IF2 Register set.
Direction = Write: The Data Bytes 4–7 will be transferred from the IF1/IF2 Register set to the
message object addressed by the Message Number (Bits [7:0]).
Note:
The duration of the message transfer is independent of the number of bytes to be
transferred.
15
Busy
Busy flag.
0
No transfer between IF1/IF2 Register set and Message RAM is in progress.
1
Transfer between IF1/IF2 Register set and Message RAM is in progress.
This bit is set to 1 after the message number has been written to bits [7:0]. IF1/IF2 Register set
will be write-protected. The bit is cleared after read/write action has finished.
14
DMA Active
Activation of DMA feature for subsequent internal IF1/IF2 update.
0
DMA request line is independent of IF1/IF2 activities.
1
DMA is requested after completed transfer between IF1/IF2 Register set and Message RAM.
The DMA request remains active until the first read or write to one of the IF1/IF2 registers. An
exception is a write to Message Number (Bits [7:0]) when DMA Active is 1.
Note:
Due to the auto reset feature of the DMA Active bit, this bit has to be separately set for
each subsequent DMA cycle.
13-8
Reserved
0
These bits are always read as 0. Writes have no effect.
7-0
Message Number
Number of message object in Message RAM that is used for data transfer.
0
Invalid message number.
1h-40h
Valid message numbers.
41h-FFh
Invalid message numbers.
Note:
When an invalid message number is written to the IF1/IF2 Command Register that is
higher than the last implemented message object number, a modulo addressing will occur. For
example, when accessing message object 33 in a DCAN module with 32 message objects only,
the message object 1 will be accessed instead.