Time-stamping of CAN messages

CiA has started to develop a specification on time-stamping CAN messages. In particular, in real-time applications it is required to know when a message has been transmitted and when it has been received.

End of last year, CiA has established the Task Force Time-stamping. The next meeting is scheduled for February 15, 2016. Location is the CiA office in Nuremberg (Germany). In general, there are different options to capture the time: You can time-stamp at the sample-point of SOF or at the sample-pint of the last bit of EOF.

The hardware-based time-stamping function should provide a free-running counter that is used to take the time-stamps. It is proposed that the free-running counter counts clock cycles, but shall not count bit-times. The resolution should be at least 1 µs. The width of the counter and the time-stamp registers should be 32 bit. If an optional 16-bit resolution is supported, then the resolution of the free-running counter should be at least 10 µs.

The automotive prefers an EOF-capturing, while TTCAN time-stamps the SOF. There is also a third option for CAN FD: measuring the time at the FDF bit, eventually more precious as at the SOF bit. The EOF approach is compliant with todays software solutions and doesn’t require any additional specifications in Autosar. If you like to participate in the development of the CiA 603 specification please contact CiA office by email (secretary(at)can-cia.org).