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Can you explain the relationship between writing timing and waveform?

Latest Updated:03/26/2009

Question:

The application note, "14-Bit PWM Function Based Variable Duty-Cycle Pulse Output" states that there may be occasions when a normal PWM waveform will fail to be output due to the timing needed to overwrite the PWM data register. Please explain the relationship between writing timing and waveform.

Answer:

Standard pulses are formed by the use of a counter in the PMW wave-forming section, in other words, by securing compare match between the value of the counter (TCNT) and the value of the compare match register corresponding to the standard pulse width. In some cases, rewriting the PWM register may generate abnormal waveforms, because the value of compare match register is changed during operation.
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