Rainbow Electronics CAN интерфейс - Manual (Page 47)

BOSCH
ROBERT BOSCH GmbH, Postfach 300240, D-7000 Stuttgart 30
Sep. 1991
Part B - page 45
Base ID
The Base ID consists of 11 bits. It is transmitted in the order from ID-28 to ID-18. It
is equivalent to format of the Standard Identifier. The Base ID defines the Extended
Frame’s base priority.
Extended ID
The Extended ID consists of 18 bits. It is transmitted in the order of ID-17 to ID-0.
In a Standard Frame the IDENTIFIER is followed by the RTR bit.
RTR BIT ( Standard Format as well as Extended Format )
Remote Transmission Request BIT
In DATA FRAMEs the RTR BIT has to be ’dominant’. Within a REMOTE FRAME the
RTR BIT has to be ’recessive’.
In an Extended Frame the Base ID is transmitted first, followed by the IDE bit and the
SRR bit. The Extended ID is transmitted after the SRR bit.
SRR BIT ( Extended Format )
Substitute Remote Request BIT
The SRR is a recessive bit. It is transmitted in Extended Frames at the position of the
RTR bit in Standard Frames and so substitutes the RTR-Bit in the Standard Frame.
Therefore, collisions of a Standard Frame and an Extended Frame, the Base ID (see
’Extended IDENTIFIER’ below) of which is the same as the Standard Frame’s Identifier,
are resolved in such a way that the Standard Frame prevails the Extended Frame.
IDE BIT ( Extended Format )
Identifier Extension Bit
The IDE Bit belongs to
- the ARBITRATION FIELD for the Extended Format
- the Control Field for the Standard Format
The IDE bit in the Standard Format is transmitted ’dominant’, whereas in the Extended
Format the IDE bit is recessive.
CONTROL FIELD ( Standard Format as well as Extended Format )
The CONTROL FIELD consists of six bits. The format of the CONTROL FIELD is
different for Standard Format and Extended Format. Frames in Standard Format
include the DATA LENGTH CODE, the IDE bit, which is transmitted ’dominant’ (see
Data Frame