I am quite new to to Texas piccolo and trying to understand the ePWM system - I have 2 queries:-
1) For the counter compare module why is CMPA register accesssed via EPwmxRegs.CMPA.half.CMPA
where as CMPB register is accessed via EPwmxRegs.CMPB
I don't understand what this half register business is?
2) If you set PWMxB to a certain action using the Action Qualifier Submodule and then set, say, complementary outputs in the dead band generator will PWMxB output be overridden by the deadband output? i.e. anything set on PWMxB by action qualifier has no effect.
For compare register CMPA is a Union of CMPA:CMPAHR, where CMPAHR ia a extension register for HRPWM compare (8 bits) please refer to TMS320x2802x, 2803x Piccolo High Resolution Pulse Width Modulator (HRPWM) reference guide for more information on high resolution operation with CMPAHR.
On the other hand CMPB does not have high resolution extension capabilities, Finer time granularity control or edge positioning is achieved using extensions to the Compare A.
Please refer to Figure 2 in the above mentioned (HRPWM) reference guide where it shows the relationship between one coarse system clock and edge position in terms of MEP steps, which are controlled via an 8-bit field in the Compare A extension register (CMPAHR).
Hope this helps,
On your other dead band question
Input Source Selection:
The input signals to the dead-band module are the EPWMxA and EPWMxB output signals from the action-qualifier. Please refer to Figure 31. Configuration Options for the Dead-Band Submodule in TMS320x2802x, 2803x Piccolo Enhanced Pulse Width Modulator (ePWM) Module.
In the DBCTL register Bit 5 controls the S5 switch and bit 4 controls the S4 switch refered as the IN_MODE. Based ont he switch setting you choose which signal falls throught he RED and FED lines to be furthur sent to toher submodules like chopper and Trip Zone.
you also have an option to bypass deadband submodule.
Ok thank you Mahesh.
So what I stated in question 2 is correct if DBCTL[IN_MODE] = 0.
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