SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
If the Global Period Enable (GLOBAL_PERIOD_EN) bit is set in DPWMCTRL1 of a DPWM module, it will use the value in PWMGLBPRD for its period. This can be used to change the periods of multiple DPWMs with one C statement. This is useful for frequency dithering. Note that the period change takes effect at the end of the previous period. If DPWMs are out of phase, the frequency change will take place at a different time for each DPWM.
Also note that the if the Filter is using the Period from the DPWM for calculations, it will still use the DPWM Period Register even if the Global Period is enabled. So to use the Global Period, it is necessary to use the KCOMP register as a multiplier and to change both the Global Period Register and the KCOMP register at the same time. In fact, a careful sequence should be followed:
If the period is increasing – first change the Global Period Register, then wait 1 period, then change the KCOMP. This sequence guards against dead time violations.
For the same reason, when decreasing the period, change the KCOMP first.
For any frequency change, the order of changes should be carefully designed based on the actual topology and IC configuration.