DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

3.3.2 Remote Frames
Remote Frames are used for receivers to request information from another node. Remote
Frames are often sent out on a regular schedule to request updates from sensors. The Remote
Frame is the same as a Data Frame with two exceptions: in a Remote Frame there is no Data
Field, and contrary to a Data Frame where the RTR bit is always transmitted dominantly (RTR =
‘0’), the RTR bit of a Remote Frame is recessive (RTR = ‘1’). The RTR bit is considered part of
the bitwise arbitration, so a Data Frame will always win arbitration in the unlikely event that
both a Data Frame and a Remote Frame with the same Message Identifier are being transmitted
at the same time. This is due to the dominant RTR bit following the Message Identifier. This is
reasonable since a request for data should not take precedence over the data being requested.
Figure 3.5 shows the structure of the Remote Frame for both Standard Data Frames and
Extended Data Frames.
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