SFO.lib并不是可有可无的东西，他能够优化HRPWM，利用闲置资源，同步好各路资源的利用，有很多好处，或许在只用一二根HRPWM而且是在慢速时可以不使用它。具体在何时使用SFO.LIB请参考下面的介绍。 MEP_SF是动态变化，而且变化的很快，随系统的时钟和DSP执行环境变化，在100MHZ的时钟环境下变化速度是180ps.
If one of the ePWM modules is not used in HRPWM mode, then it can be dedicated to run the SFO diagnostics for the modules that are running HRPWM mode. Here the single MEP_SF value obtained can be applied to other ePWM modules. This assumes that all HRPWM module’s MEP steps are similar but may not be identical. The ePWM module that is not active in HRPWM mode is still fully operational in conventional PWM mode and can be used to drive PWM pins. The SFO function only makes use of the MEP diagnostics logic. The other ePWM modules operating in HRPWM mode incur only a 3-cycle minimum duty limitation. If the application requires all ePWM modules to have HRPWM capability (i.e., MEP is operational), then the
SFO_MepEn(n) function should run for each of the active ePWM modules with HRPWM capability.
· In the above case, a 6-cycle MEP inactivity zone exists at the start of the PWM period. See Section 2.3.3
on duty cycle range limitation.
· If all ePWM modules are using the same TBCLK prescaler, then it is also possible to run the
SFO_MepEn(n) function for only one ePWM module and to use the SFO return value for the othermodules. In this case only one ePWM module incurs the 6-cycle limitation, and remaining modules incur only a 3-cycle minimum duty limitation. See “Duty cycle limitation” section. This assumes that all HRPWM module’s MEP steps are similar but may not be identical.
http://focus.ti.com.cn/cn/lit/ug/spru924c/spru924c.pdf 第17~20页
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