Hatem,

the approach of "drawing" the waveforms is ok. the maximum frequency is dependant of your clock.

You can vary the frequency of your waveforms varying the delay between each point. E.g. for you square wave, lets say that you have hundred 0s and hundred 1s stored. If you take 1ms to send each point to the DAC your waveform will have a (100*1ms + 100*1ms) period or 5Hz. But if you send the points faster, like 10us, you'll have (100*10us + 100*10us) period or 500Hz.

Why the counter? You can just select the appropriate addresses of your eprom and use the data output to feed the DAC

I don´t see the need of dividing the waveforms in quarters, as you won't combine these quarters to generate other types of waveforms.

hth

orlando