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

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

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Arbitration FieldThe Arbitration Field in the Extended Format Data Frame is longer to<br />

accommodate the 29-bit Message Identifier. Over 536 million (2 29 ) unique messages are<br />

possible using the Extended Format. The Standard Message Identifier is identical to the<br />

Message Identifier Field in the Standard Data Frame Format. It is 11 bits long and<br />

contains the most significant bits of the 29-bit identifier. The Substitute Remote Request<br />

Field (SRR) bit replaces the RTR bit in the Standard Data Frame. Its sole purpose is to<br />

be a placeholder so that the Identifier Extension bit remains in the same location as it is in<br />

the Standard Data Frame Format. This bit is always transmitted recessively. The RTR<br />

bit for the Extended Data Frame Format has been moved to the end of the Arbitration<br />

Field. If the IDE bit is recessive, then the frame is an Extended Data Frame Format<br />

otherwise the frame is a Standard Data Frame Format. The Extended Message Identifier<br />

Field adds another 18 bits on to the Standard Message Identifier. This brings the total<br />

number of identifier bits to 29. The RTR bit in an Extended Data Frame Format is<br />

identical to the RTR bit in the Standard Data Frame Format. It indicates whether the<br />

frame is a Data Frame or a Remote Frame. This bit value will be a dominant (‘0’) bit for<br />

a Data Frame and a recessive (‘1’) bit for a Remote Frame.<br />

Control FieldThe Control Field in the Extended Data Frame Format contains two<br />

reserved bits and the DLC bits. The reserved bits, r1 and r0, are unused and must be<br />

transmitted dominantly. The DLC bits in an Extended Data Frame are identical to those<br />

used in a Standard Data Frame.<br />

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