CCS/TMS320F28377S: regarding ramp generation using ramp generator in comparator module

1) in cmpss digital fiilter example we are seeing that the dac is being used but why is the choice for compdacctl.swloadsel left out 

SWLOADSEL is by default 0. So adding it to the example and setting it to 0 doesn't change anything. Also, keep in mind the examples are written as starting point for customers and don't contain everything needed to get a fully working application. However, the examples should work as is.

2) i'm trying to use the ramp generator to generate a ramp wave of 10khz frequency , how can i figure out the value of rampmax ref and rampdacvala ,inorder to get the 10 khz ramp.

This will be a simple equation of 2 unknowns which means you will have to set 1 value to find the other. 10KHz is 0.1ms period. You will need to set rampmaxref and decval to values that will allow the rampgen to complete ramping down within 0.1ms.

This works out to something like: (rampmaxref * sysclk_period)/decval = ramp_frequency_period. If you'd rather work in frequencies and not periods, you can easily convert the equation to that instead. rampmaxref and decval are the 2 unknowns. Set one to find the other. You'll most likely have more restriction on rampmaxref because that sets the peak value of the ramp.

3)the selection of rampsource from pwmsync events , on what basis should we select it .

If you are asking which pwm to use as the rampsource, you can use any pwm.

4) how can we control the magnitude of the ramp generated , is it based on the rampmaxref ? if so is there a proportion of the value with the desired voltage?

Yes, max value of the ramp is rampmaxref.

5) is epwm8 initiation necessary in cmpss_asynch example?

Yes.