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CAN stands for Controller-Area-Networking. The CAN-TRANSCEIVER is the final stage of a can-device. Its purpose is to rectify the logical signals of a can-controller according to the ISO 11898 standard.
This circuit describes the principles of how the physical signals CAN-high and CAN-low are beeing generatet.The CAN-high signal is represented by the blue line, CAN-low by the green line. The clock-signal generator represents the CAN-Tx from the controller. I left
out the comperator-stage for the CAN-Rx on purpose...
The CAN physical layer is well described in the ISO 11898:
- Data link layer,
- High speed medium access unit,
- Low speed, fault tolerant, medium dependent interface,
- Time-triggered communication.
Some main characteristics of CAN :
- bus-access: CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)
- bit-protocoll: NRZ (Non Return to Zero)
- Tx low -> bus recessive, transmitts logic 1
- Tx high -> bus dominant, transmitts logic 0
- Hamming-Distance: 6
Today almost all CAN devices do support a basic message layer (CAN-layer or layer2), allowing to create a proprietary
protocoll for data exchange. The higher layer protocolls CiA CANopen and SAE J1939 are both based on the basic
message layer according to ISO 11898. The today actual CAN specification is available in version 2.b, supporting
11-bit and 29-bit CAN-ID.
CAN devices are available from many different suppliers. For example, the company ifm-electronic provides
costefficient and robust automation-systems for use in mobile machinery, supporting CAN , CANopen, Can-Safety and J1939.
A lot of books are already written about CAN, however one became my favorite:
"A Comprehensible Guide to Controller Area Network", published by Copperhill media...
THIS CIRCUIT IS DEMONSTRATION / EDUCATION PURPOSE ONLY!
31.08.2018: See also CAN_TRANSCEIVER_2
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