C2000WARE: Questions about EPwm X-Bar and triggering faults with Digital Compare Module

Hi,

I am working through the method of a fault triggering off my PWM signals in either CBC or OSHT mode. I plan to measure three voltages and two currents with the ADC pins that are also connected to the CMPSS positive inputs to turn off the PWM when signals higher than the DAC reference are present. I want the voltages to all be OSHT mode and currents to be all CBC mode.

My questions about these modules are as follows:

In example programs on TI C2000Ware, the designer configures GPIO signals for the trip zone. What is the purpose of using GPIO signals? 
If I understand correctly, the comparator will be high when a fault is detected, which we can route to TRIP4-TRIP12 of the EPwm X-Bar, and generate DCAEVT and DCBEVT and use these to force the PWM to a low-state. I don't see why there is a need for the GPIO signals, doesn't the EPwm X-bar achieve the required functionality on its own? Are there for if we are not using the digital sub-compare module?

What is the benefit of using the sub-compare module, then? It seems you can force PWM low using:

 EPwm1Regs.TZCTL.bit.TZA = 0x10 // On trip, force EPWM1A to a LOW state

EPwm1Regs.TZCTL.bit.TZB = 0x10; // On trip, force EPWM1B to a LOW state

or you could use the sub-compare module and perform:

EPwm1Regs.TZCTL.bit.DCAEVT1 = 0x10; // On trip, force EPWM1A to a LOW state
EPwm1Regs.TZCTL.bit.DCBEVT1 = 0x10; // On trip, force EPWM1B to a LOW state

Do they not just perform the exact same function? 

How do you program the PWM X-Bar, Digital Compare module and Trip zone to have both cycle-to-cycle and One shot trips? It appears to me that if you OR together four comparators, two which are OST and two which are CBC, there is no way to differentiate between which is which by the time you reach the sub-compare module, DCAH/DCBH will be set and it's after this point that you set the events to either one-shot or cycle by cycle fault limiting! So it seems to me that you can only set your PWM module to either be CBC trip, or OST trip,  but not both. Is this correct?

Finally, how does one perform the above trip functionality if the input is a differential signal from the 16-bit ADC? Surely you'd want to apply the differential ADC voltage to the comparator subsystem, but from the data sheet, it looks like this is not possible. Would you have to not use the internal DAC reference and instead supply the differential signal outputs to the positive and negative inputs of a single comparator? The TRM does not outline how to detect faults in a differential input signal.

Thanks,

Joel