The document provides an introduction to vehicle Controller Area Network (CAN) protocols. It discusses the history and features of CAN, including its low data overhead and flexibility. It describes the different types of CAN networks for various vehicle systems and functions. It outlines the four main frame types used in CAN communications: data, remote, error, and overload frames. It explains the structure and purpose of data frames, including standard and extended frame formats. It also describes error handling and types of errors that can occur on a CAN network.

1. VEHICLE NETWORKS Introduction to CAN Joseph Holly [email_address]

2. NETWORK PROTOCOLS There are multiple vehicle networking protocols, each with its own history and function. The most common protocol in light vehicles is Controller Area Network ( CAN ). Even a single vehicle is likely to contain multiple networks and multiple protocols.

6. FOUR FRAME TYPES - DATA - REMOTE - ERROR - OVERLOAD

7. DATA Frame Two Types: STANDARD and EXTENDED  STANDARD - 11-bit identifier  EXTENDED - 29-bit identifier

8. Structure of a DATA FRAME START OF FRAME (SOF) - Indicates a new transmission to all receiving nodes - Also used by all receiving nodes for synchronization SOF ARB DATA ACK CRC CONTROL EOF

11. Structure of a DATA FRAME DATA FIELD – Actual message data SOF ARB DATA ACK CRC CONTROL EOF

12. Structure of a DATA FRAME CYCLIC REDUNDANCY CHECK (CRC) – Error-trapping method used by controller to verify successful data transmission. Every data frame is validated, retransmitted if necessary. SOF ARB DATA ACK CRC CONTROL EOF

13. Structure of a DATA FRAME ACKNOWLEDGEMENT FIELD – Field in which receiving nodes signal that message was properly received. If ACK is not received, originating node retransmits message. SOF ARB DATA ACK CRC CONTROL EOF

14. Structure of a DATA FRAME END OF FRAME (EOF) - Indicates end of transmission from originating node - Signals beginning of Intermission period. SOF ARB DATA ACK CRC CONTROL EOF

15. REMOTE Frame Used by any node to request data from any other node. Same structure as Data Frame, except: - Remote Frame has no message in Data Field - Control Field used to indicate size of expected return data

16. ERROR Frame Two Types: ACTIVE and PASSIVE When a transmitting node sends an Error Frame, it is detected by all the other nodes on the network. They respond by sending their own error flags.

17. Structure of an ERROR FRAME ERROR FLAG ERROR DELIMITER ERROR FLAG – Unique message sent by the node detecting an error. Any receiving node will respond with its own error flag transmission. ERROR DELIMITER – “ quiet” period following initial error flag transmission.

18. ERROR TYPES Greater-than-allowed number of consecutive bits of the same polarity trigger an Error Flag. Stuff Error Sending nodes verify their own transmissions and re-send if there’s an inappropriate bit. Bit Violation A dominant bit in EOF, Interframe Space, CRC Delimiter or ACK Delimiter triggers an Error. Form Violation Every receiving node should acknowledge message. If no ACK received, originating node generates Error Flag and re-sends message. ACK Error If the checksum fails at any node, the Error Flag will cause the originating node to re-send. CRC Error

19. OVERLOAD Frame Structurally similar to the Error Frame, but sent during the Intermission period. Originally used to allow an early ECU chip to keep up with network traffic. Not usually needed by modern processors.

20. CAN NETWORKS ERRORS DETECTED (none shown) MSG DATA (shown in hex) ARB ID MSG LENGTH CAN DATA on viewing software