20-08-2013, 03:06 PM
CAN BUS (Controller Area Network)
CAN BUS .ppt (Size: 352.5 KB / Downloads: 23)
Overview
CAN (Controller Area Network) is a serial bus system used to communicate between several embedded 8-bit and 16-bit microcontrollers.
It was originally designed for use in the automotive industry but is used today in many other systems (e.g. home appliances and industrial machines).
Highest Baud Rate is 1Mbit.
CAN uses a message oriented transmission protocol.
There are no defined addresses, just defined messages.
Data Information – Frame Format
SOF – Start of Frame
Identifier – Tells the content of message and priority
RTR – Remote Transmission Request
IDE – Identifier extension (distinguishes between CAN standard,11 bit identifier, and CAN extended, 29 bit identifier.)
DLC – Data Length Code
Data – holds up to 8 bytes of data
CRC – “Cyclic Redundant Check” sum
ACK – Acknowledge
EOF – End of Frame
IFS – Intermission Frame Space. Minimum number of bits separating consecutive messages.
Data Information – Error detection
If one or more errors are detected, the transmission is aborted. This prevents all other stations or nodes from accepting the message.
Re-transmission is automatic. If errors continue, then the station or node may switch itself off to prevent the bus from being tied up.
Error detection is done on two levels:
Message level
Bit level
Summary
CAN (Controller Area Network) is a serial bus system used to communicate between several embedded 8-bit and 16-bit microcontrollers
Data Information
Frame Format
Protocol – message oriented
Error Detection
Message level (CRC, frame check, ACK errors)
Bit level (monitoring, bit stuffing)
Implementations
Basic CAN
Full CAN
FIFO
Enhanced Full CAN
Over 20 different chip manufacturers produce microcontrollers with on-chip CAN interfaces including Cygnal, Intel, and Motorala.