Time Quanta Clock

The time quanta clock (TQ_CLK) is derived from the controller reference clock (CAN_REF_CLK) divided by the baud rate prescaler (BRP).

t_{TQ_CLK} = t_{CAN_REF_CLK} * (can.BRPR[BRP] + 1) freqT_{Q_CLK} 
= freq_{CAN_REF_CLK} / (can.BRPR[BRP] + 1)

t_{SYNC_SEGMENT} = 1 * t_{TQ_CLK} t_{TIME_SEGMENT1} 
= t_{TQ_CLK} * (can.BPR[TS1] + 1) t_{TIME_SEGMENT2} 
= t_{TQ_CLK} * (can.BPR[TS2] + 1) t_{BIT_RATE} 
= t_{SYNC_SEGMENT} + t_{TIME_SEGMENT1} + t_{TIME_SEGMENT2} freq_{BIT_RATE} 
= freq_{CAN_REF_CLK} / ((can.BRPR[BRP] + 1) * (3 + can.BTR[TS1] + can.BTR[TS2]))

 

TIP:   A given bit-rate can be achieved with several bit-time configurations, but values should be selected after careful consideration of oscillator tolerances and CAN propagation delays. For more information on CAN bit-time register settings, refer to the CAN 2.0A, CAN 2.0B, and ISO 11898-1 specifications.