CAN

Overview

Controller Area Network (CAN) Bus Protocol Information. The ISO-11898:2003 Standard, with the standard 11-bit identifier, provides for signaling rates from 125kbps to 1 Mbps. The standard was later amended with the “extended” 29-bit identifier.

Packet Details

11-bit packet layout

• SoF - Start of Frame (1 bit)
• 11-bit ID - (aka Arb ID) Also sets Priority. Lower is higher prio
• RTR - Remote Transmission Request (1 bit)
• IDE - ID Extension (1 bit)
• Reserved - (1 bit)
• DLC - Data Length Code (4 bits) Length of data
• Data - Up to 8 bytes (Some Systems pad with 0s others don't)
• CRC - 2 bytes (15 bits plus delimeter) CRC
• ACK - 2 bits (1 is ack, 2nd is delminter)
• EOF - 7 bits End of Frame
• IFS - 7 bits Interframe space

29-bit packet layout

• SoF - Start of Frame (1 bit)
• 11-bit ID - (aka Arb ID) Also sets Priority. Lower is higher prio
• SRR - Substitute Remote Request (1 bit)
• IDE - ID Extension (1 bit)
• 18-bit ID -
• RTR - Remote Transmission Request (1 bit)
• Reserved - (2 bits)
• DLC - Data Length Code (4 bits) Length of data
• Data - Up to 8 bytes (Some Systems pad with 0s others don't)
• CRC - 2 bytes (15 bits plus delimeter) CRC
• ACK - 2 bits (1 is ack, 2nd is delminter)
• EOF - 7 bits End of Frame
• IFS - 7 bits Interframe space

See Also

• http://www.ti.com/lit/an/sloa101a/sloa101a.pdf TI - Introduction to the Controller Area Network
• VRL Hive13