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TMS320F28035: PWM SYNCI/SYNCO Delay

Stuart Baker
Genius 10620 points
Part Number: TMS320F28035

The following thread references the SYNCI/SYNCO delay timing that applies to the F2806x family (and presumably the F2803x family as well):

We are wondering if it is predictable as to whether or not it is 6 or 7 clocks for the purpose of synchronizing 128 devices in series.  The difference between 6 or 7 clock cycles adds up quite a bit in the worst case (128 clocks total).  My presumption is that the difference between 6 or 7 clocks has everything to do with synchronizing the incoming asynchronous signal with the internal clock.  If this is the case, the probability of 6 or 7 clocks should be 50%.  Please advise.

Thanks,

Stuart

  • 0
    TI__Mastermind 42195 points
    Stuart,
    I am looking into this, and will try to get you a direct answer.

    Regards,
    Cody
  • 0
    TI__Mastermind 42195 points

    Stuart,

    It will be 6-7 clocks, the variation in this number is due to the synchronizing as you have correctly assumed. This 6-7 clock delay is only between an external pulse and SYNCI, it does not take affect between 2 ePWM modules. If you sync ePWM1,2 and 3 all to the same external pulse ePWM1,ePWM2 and ePWM3 will each experience a delay of 6-7 clocks from the input pulse. This error does NOT stack if you sync more than one ePWM to the same external pulse, ie. if ePWM2 is second in the sync chain it will NOT delay 12-14 cycles, it will have a delay of 6-7.

    I know that paragraph was rather redundant, but I hope it go t the point across one way or another.

    Additionally this design would benefit from a “parallel” sync, send one sync pulse to all devices at the same time. If you ar syncing across multiple device I would also recommend that your master sync signal is equidistant from each of the device to reduce clock skew.

    Regards,

    Cody