Image Processing Reference
In-Depth Information
SOF: Start of frame
EOF: End of frame
Ack: Acknowledgment
Inter: Intermission
Applicatio
n
data
CRC field
Ack
EOF Inter
SOF
Header
... Idle
Idle ...
18 bits
Standard CAN (2.0A)
0..8 bytes
15 bits
3 bits
7 bits
3 bits
1 bit
FIGURE .
Format of the CAN .A data frame. (From Navet, N., Song, Y.Q., Simonot-Lion, F., and Wilwert, C.,
Proc. IEEE
., (), , . With permission.)
0: Data frame
1: Request frame
Identifier
DLC
1
R
T
R
0 or 1
0 or 1
0
11 bits
3 bits
4 bits
FIGURE .
Format of the header field of the CAN .A data frame. (From Navet, N., Song, Y.Q., Simonot-Lion,
F., and Wilwert, C.,
Proc. IEEE
., (), , . With permission.)
Edges are generated into the outgoing bit stream in such a way to avoid the transmission of more than
a maximum number of consecutive equal-level bits ( for CAN). he receiver will apply the inverse
procedure and de-stuff the frame. CAN requires the physical layer to implement the logical “and”
operator:ifatleastonenodeistransmittingthe“”bitlevelonthebus,thenthebusisinthatstate
regardless if other nodes have transmitted the “” bit level. For this reason, is termed the dominant
bit value while is the recessive bit value.
The standard CAN data frame (CAN .A, see Figure .) can contain up to bytes of data for an
overall size of, at most, bits, including all the protocol overheads such as the stuff bits. he sections
of the frames are
•
Header field (see Figure .), which contains the identifier of the frame, the remote trans-
mission request (RTR) bit that distinguishes between data frame (RTR set to ) and data
request frame (RTR set to ) and the data length code (DLC) used to inform of the number
of bytes of the data field.
•
Data field having a maximum length of bytes.
•
bit cyclic redundancy code (CRC) field which ensures the integrity of the data
transmitted.
•
Acknowledgment field (Ack). On CAN, the acknowledgment scheme solely enables the
sender to know that at least one station, but not necessarily the intended recipient, has
received the frame correctly.
•
End-of-frame (EOF) field and the intermission frame space which are the minimum
number of bits separating consecutive messages.
