CAN
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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