Knowledgebase
CANbus V2.0A and V2.0B, 11 and 29 bits?
Posted by Squarell Technology on 25 October 2013 10:39 AM

If you are digging into CANbus you will find a lot of protocols and technology features.

We like to give you a little guide in this CANbus world and give some comments on the main aspects.

CANopen or Device NET:
These are protocols for CANbus.
• CANopen is used in machinery.
• DeviceNET is used in harsh environment equipment.
• J1939 is used for automotive environments.

CANopen and DeviceNet are not used as a standard in the automotive world, so if you find equipment based on CANopen like interfaces, data loggers, sensor devices or anything else, it is not compatible with the FMS CANbus / J1939 protocol. To make proper use of such devices, J1939 support must be provided by the supplier.

11 and 29 bits
FMS CANbus / J1939 protocol is a 29 bits protocol.
CANopen and DeviceNet are 11 bits protocols.

The 11/29 bits relate to the identification techniques of messages. A 11 bits protocol uses 11 bits to specify a message (2^11=2048 message ID’s). A 29 bits protocol has a wider range of dressing (2^16=65536 message ID’s) and uses source and destination addresses in its message ID. Over a CANbus 11 and 29 bits can be sent without interfering each other. Squarell CANbus products support 11 and 29 bits messages.  

You do not have to care about 11 or 29 bits. Make sure you read our J1939 documentation to know about the FMS CANbus / J1939 protocol.

It is also referred as CAN V2.0A = 11 bits, CAN V2.0B = 29 bits.


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