Docan Diagnostic communication over controller Area Network diagnostic communications Controller regional networks
CAN Controller Area Network controller regional networks
ECU electronic control Unit electronic controls
FMI Failure mode indicator fail mode indicator
OBD On-board diagnostics onboard diagnostics
SPN suspect parameter number of arguments not trusted
WWH-OBD World-wide harmonized on-board diagnostics global coordinated onboard diagnostics
Two frame format
Types and uses of frames
Data frame remote Frame Error frame overload frame frame interval
Data frame
The data frame is composed of 7 segments.
The composition of the data frame is shown in Figure 16.
(1) Frame start
A segment that represents the beginning of a data frame.
(2) Arbitration section
The segment that represents the priority of the frame.
(3) Control Section
Represents the number of bytes of data and the segment that holds the bits.
(4) Data segment
The contents of the data, which can send 0~8 bytes of data.
(5) CRC section
Check the segment of the frame for transmission errors.
(6) ACK segment
Indicates a segment that confirms normal reception.
(7) End of frame
Data frames are composed of multiple segments
Arbitration Section
The ID of the standard format has 11 bits. From ID28 to ID18 are sent sequentially. Disallow high 7 bits to be recessive. (Prohibit setting: ID=1111111XXXX)
The ID of the extended format has 29 bits. The base ID is from ID28 to ID18, and the extension ID is represented by ID17 to ID0. The base ID and the standard format have the same ID. Disallow high 7 bits to be recessive. (Prohibit setting: Basic id=1111111xxxx)
Reserved bits (r0, R1)
Reserved bits must all be sent at a dominant level. But the receiver can receive explicit, implicit and any combination of levels.
* * Data length code (DLC)
The correspondence between the data length code and the number of bytes of data is shown in table 8.
The number of bytes of data must be 0~8 bytes. However, the receiver's case for DLC = 9~15 is not considered an error.
CRC sequence
CRC sequence is based on the CRC value generated by the polynomial, the calculation range of CRC includes frame start, arbitration segment, control section, data
Paragraph
The receiver computes the CRC value and compares it with the same algorithm, and informs the error when it is inconsistent.
ACK segment of the sending unit
The sending unit sends a 2-bit recessive bit in the ACK segment.
* * The ACK segment of the receiving unit
The unit that receives the correct message sends the dominant bit in the ACK slot (ACK slot), notifying the sending unit that the normal receive ends. This is called "hair
Send Ack "or" return ack ".
2. Standard can protocol
; 00 01 02 03 04 05 06 07 08 09 10 11 12
CMD:0D Geneva 3E 00 55 55 55 55 55
ret:0d Geneva 7F 7E xx aa aa AA AA
Frame length + frame mode + data length + frame id+ data bit
01) Frame Length: (BYE00)
02) Frame Mode: 01: Command frame 02: Data Frame (BYE01)
The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion;
products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the
content of the page makes you feel confusing, please write us an email, we will handle the problem
within 5 days after receiving your email.
If you find any instances of plagiarism from the community, please send an email to:
info-contact@alibabacloud.com
and provide relevant evidence. A staff member will contact you within 5 working days.
