PWM停止

刘东君

我想问下PWM如何停止输出！
我这用了2路PWM输出，同一个定时器T3，通道是CH1/CH2如何停止一路输出，另一路有输出呢，停止后该引脚输出什么？ 还是说用TIM_SetCompare2（TIM3，0）来控制？

1759

我也有一样的问题

cjsyrzy

TIM_SetCompare2 这个控制CH2的比较值，有些情况可以停止PWM，比如TIM_OCMode_PWM1+TIM_OCPolarity_High+TIM_CounterMode_Up，停止后该引脚电平由 TIM_OCMode+TIM_OCPolarity+TIM_CounterMode 决定

聚东风

你把CCRx设置为0不就是停止输出了吗?你把CCER中的相应通道设置为0不就是关闭输出了吗

cjsyrzy

110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNT<TIMx_CCR1
else inactive. In downcounting, channel 1 is inactive (OC1REF=‘0) as long as
TIMx_CNT>TIMx_CCR1 else active (OC1REF=1).
111: PWM mode 2 - In upcounting, channel 1 is inactive as long as TIMx_CNT<TIMx_CCR1
else active. In downcounting, channel 1 is active as long as TIMx_CNT>TIMx_CCR1 else
inactive.

输出电平 OCx = OCxREF + Polarity

PWM1:
upcounting:
if (TIMx_CNT <   TIMx_CCRx) OCxREF = 1; else OCxREF = 0;
downcounting:
if (TIMx_CNT <= TIMx_CCRx) OCxREF = 1; else OCxREF = 0;
if (TIMx_CNT >   TIMx_CCRx) OCxREF = 0; else OCxREF = 1;

PWM2:
upcounting:
if (TIMx_CNT <   TIMx_CCRx) OCxREF = 0; else OCxREF = 1;
downcounting:
if (TIMx_CNT <= TIMx_CCRx) OCxREF = 0; else OCxREF = 1;
if (TIMx_CNT >   TIMx_CCRx) OCxREF = 1; else OCxREF = 0;

当CNT的值变化成CCR的值的瞬间，REF翻转。