DCAN Control Registers
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SPNU563A–March 2018
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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.
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