CAN Bit Timing Requirements

The CAN protocol provides for programming of the bit rate, and the number and location of data samples in a bit period. Optimization of these parameters guarantees message synchronization and proper error detection at the extremes of oscillator tolerance and propagation delay. Modifications to the CAN protocol have redefined the limiting conditions for proper synchronization and error detection. These conditions have been analyzed and a comprehensive set of equations describing the resulting bit timing requirements has been developed. A step by step method for calculating optimum CAN bit timing parameters for a given set of system constraints is presented. This paper was developed in support of the SAE J2284 CAN High Speed Implementation Task Force and the results incorporated into its proposed standard.