Presentation on theme: "Jonathan Meed Alexander Basil. What is CAN (Controller Area Network) CAN is a multi-master serial bus Developed by Bosch for automotive applications in."— Presentation transcript:
What is CAN (Controller Area Network) CAN is a multi-master serial bus Developed by Bosch for automotive applications in early 1980s o Released publicly in 1986 o Became ISO standard in 1993 o Is now required in all cars in the USA Used for connecting multiple separate electronic systems 2
Figure 1 - Typical CAN implementation in a car  3
U CAN 2 CAN implementation often requires additional hardware to generate LVDS MCP2551 7
Bus Idle Inter- missio n SOFSOF EOFEOF Address Field Control Field Data Field CRC Field ACK Field Stack Frame Message Figure 4. CAN Message bit partitioning. Bus Idle Inter- missio n for CAN 2.0A SOFSOF EOFEOF Address Field Control Field Data Field CRC Field ACK Field Start of frame (low bit) Address (arbitration) Control (data length, reserved bits) Data Cyclic Redundancy Check (error checking) Acknowledge End of frame Intermission (time between frames) 1 bit12 bits6 bits0-8 bytes16 bits2 bits 7 bits 8
Message Arbitration (same as I2C) Message includes 11-bit target address and a remote transmission bit o Lower target address value = higher priority Node transmits the target address bit-by-bit and receives other transmitted addresses o If it transmits a 1 and receives a 0, it loses arbitration Figure 5 - Arbitration example.  9
Pros and Cons Pros o Long transmission distance and low weight o Multiple masters with arbitration o Great for inter-board communication o The bus is not clocked (but requires each device on the bus to run at the same clock speed) Cons o Complex for single board or single device communications I2C and SPI are more suited for this environment o Higher cost – overhead bits and additional hardware 10
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