Rainbow Electronics CAN интерфейс - Manual (Page 44)

BOSCH
ROBERT BOSCH GmbH, Postfach 300240, D-7000 Stuttgart 30
Sep. 1991
Part B - page 42
3 MESSAGE TRANSFER
3.1 Frame Formats
There are two different formats which differ in the length of the IDENTIFIER field:
Frames with the number of 11 bit IDENTIFIER are denoted Standard Frames. In
contrast, frames containing 29 bit IDENTIFIER are denoted Extended Frames.
3.2 Frame Types
Message transfer is manifested and controlled by four different frame types:
A DATA FRAME carries data from a transmitter to the receivers.
A REMOTE FRAME is transmitted by a bus unit to request the transmission of the
DATA FRAME with the same IDENTIFIER.
An ERROR FRAME is transmitted by any unit on detecting a bus error.
An OVERLOAD FRAME is used to provide for an extra delay between the preceding
and the succeeding DATA or REMOTE FRAMEs.
DATA FRAMEs and REMOTE FRAMEs can be used both in Standard Frame Format
and Extended Frame Format; they are separated from preceding frames by an
INTERFRAME SPACE.
3.2.1 DATA FRAME
A DATA FRAME is composed of seven different bit fields:
START OF FRAME, ARBITRATION FIELD, CONTROL FIELD, DATA FIELD, CRC
FIELD, ACK FIELD, END OF FRAME. The DATA FIELD can be of length zero.
Message Transfer