SFFS779 December 2024 TMS320F28P550SJ
The microedge positioner (MEP) logic in HRPWM is capable of placing an edge in one of 255 discrete time steps. The size of these steps is 150ps. For typical MEP step size, refer to the device-specific data sheet. The MEP step size varies based on the worst-case process parameters, operating temperature, and voltage. MEP step size increases with decreasing voltage and increasing temperature and decreases with increasing voltage and decreasing temperature. Applications that use the HRPWM feature must use the MEP scale factor optimization (SFO) software function supplied by TI. The SFO function helps to dynamically determine the number of MEP steps per EPWMCLK period while the HRPWM is in operation.
The HRPWM module has a built-in self-check and diagnostic capabilities that can be used to determine the appropriate MEP scale factor value for any operating condition. TI provides a C-callable library containing one SFO function that utilizes this hardware and determines the appropriate MEP scale factor. For a given system-clock frequency at a given temperature, a known MEP scale factor value is returned by the SFO determination function. The correct system-clock frequency operation is verified by comparing the MEP scale factor value returned with the expected value.