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TMS570LS3137: Regarding the problem of HET PWM sampling not clearing

Green Deng
Expert 4490 points

Part Number: TMS570LS3137

Dear team:

My customer does PWM duty cycle and frequency sampling.

When there is an external signal, it can sample correctly and change with external changes. However, when there is no external signal, the duty cycle or frequency cannot be updated to 0, and the last sampling before the signal disappears can only be maintained.

The measurement method used by the customer is to use the function capGetSignal generated by the driver. He has used the breakpoint method to see that the sample value read from the hetram is not correct, that is, the part marked in red in the figure, the returned duty cycle and period are both No, does it need to be cleared somewhere?

Best regards

  • +1
    TI__Guru**** 200926 points

    Hi Green,

    The NHET uses PCNT to capture the input waveform. PCNT captures the counter value into the period/pulse data field [D31:D0] on the selected edge. When the overflow count is reached, PCNT stops counting. Please refer to the device datasheet to see the timing constraints on the input signal: