EXT_SYNC of PWM initial frequency settings

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EXT_SYNC of PWM initial frequency settings

Contributor II

Hi guys,

Based on NXP App note, AN4885 - eFlexPWM. The Current Reset PWM can be used using EXT_SYNC. How can I be able to change its initial frequency? The frequency in my PE settings which is shown below is not used in the PWM when there's no input signal(coming from the EXT_SYNC signal). It says in the app note code, that the initial frequency can be configured. But how?



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NXP TechSupport
NXP TechSupport

Hi, Kien,

Pls refer to the following figure, if you set the INIT_SEL=2b'00, local sync will reset the counter, in other words, if you set INIT_SEL=2b'00, the PWM signal frequency will be 120Hz.

 if you set INIT_SEL=2b'11, the EXT_sync signal will reset the PWM counter, in the case, the PWM frequency is the same as EXT_sync signal frequency.  in the case, if EXT_sync signal disappear, the PWM counter will continue to count even if it reaches to Value1 register, the PWM frequency is undetermined.

If you want to implement the scheme that the PWM outputs 120HZ signal when the EXT_sync disappears, the PWM outputs signal which is controlled by EXT_sync when the EXT_sync appears. I think it is okay, but it is complicated. You have to use AOI module to OR the EXT_sync signal and master/local sync signal as new EXT_sync signal, while set the INIT_SEL=2b'11.

Hope it can help you


XiangJun Rong


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