TM4C123GH6PM中的PWM的周期、频率怎么设置的？

TM4C123x的最高主频可以配置为80MHz。TM4C129x是120.

针对PWM的使用，参考源码：

//
// Set the PWM period to 250Hz. To calculate the appropriate parameter
// use the following equation: N = (1 / f) * SysClk. Where N is the
// function parameter, f is the desired frequency, and SysClk is the
// system clock frequency.
// In this case you get: (1 / 250Hz) * 16MHz = 64000 cycles. Note that
// the maximum period you can set is 2^16 - 1.
// TODO: modify this calculation to use the clock frequency that you are
// using.
//
PWMGenPeriodSet(PWM0_BASE, PWM_GEN_0, 64000);

//
// Set PWM0 PD0 to a duty cycle of 25%. You set the duty cycle as a
// function of the period. Since the period was set above, you can use the
// PWMGenPeriodGet() function. For this example the PWM will be high for
// 25% of the time or 16000 clock cycles (64000 / 4).
//
PWMPulseWidthSet(PWM0_BASE, PWM_OUT_0,
PWMGenPeriodGet(PWM0_BASE, PWM_OUT_0) / 4);

这里阐述的很清楚了。注意PWM定时器是16bit的，所以最大值不能大于65535，就是2的16次方减一