Hi Kai,

Thanks for your reply, To me it doesn't seem to be a problem due to distorted waveforms or zero phase shift. Let me tell me what I have done to test this. I wrote a simple small program which just fires the thyristor and does no other work. The program is a never ending super loop in this super loop I do the following.

1. Wait for change on zero cross pin i.e P3.2 [polling].
2. Start timer 0 and wait for 6 ms untill it flags.
3. Start firing the pulses using timer 1 flaging.
4. Go back to step 1.

With this simple program there is no flickering at all. Thus it rules out the possible problems of wave shape distortion and any other problems apart from my software. This test clearly indicated that there is something wrong with my software and nothing else.

I am using a good quality line filter just before I feed power to the device's transformer.

It seems something is wrong with interrupt priority or some thing else with my interrupt but can't find whats wrong.

Thanks & Regards,
Prahlad Purohit