Datasheet

DCAN Control Registers

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Table 26-24. 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-80h Valid message numbers, if 128 message objects are implemented

81h-FFh Invalid message numbers, if 128 message objects are implemented

Note: When an invalid message number is written to the IF1/IF2 Command Register which 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.

1206

Controller Area Network (DCAN) Module SPNU562–May 2014

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