GENERATION OF SINE WAVE[50Hz] USING ATmega32

Hello
I am trying to make a sine wave inverter. But i am facing a lot of troubles. At the first time i feel it might be easy to generate the sine wave using the controller because i studied that using a low pass filter at the output of the high frequency output of the controller then the square wave will become sine wave. I used a LC low pass filter. But before that i applied the square wave pulses from the controller to an H bridge using Mosfets. And i fed the output of the H bridge to LC low pass filter. But i didnt get the sine wave output. I am giving my code here. I am not sure that my program is right or wrong. But i wrote the program using my own idea. Somebody please help me to correct this..

Here is the circuit diagram of the inverter i made in Proteus..without connecting the output of AND gates to the MOSFET's gate terminals
And also the simulation result of the circuit..in Proteus CRO..
But when i connect the output of the two and gates to the gate terminals of the H bridge, the simulation stops and i am getting a window like this..

What I like most in my life is specialization and what I hate is stress. Check this IC XR2206, it is capable in producing several waveforms including sine wave with few external component. However if there are other controls you want to implement with the microcontroller, you can still incorporate the microcontroller but the IC under reference will give you a pure sine wave whose frequency ranges from 10Hz to 20kHz.

It clearly shows that Time step for Transient analysis it too low. Increase the Transient analysis step time in Proteus.

how can i increment the transient analysis step time.. where is the option in Proteus.. if i increment the transient time will the waveform will appear in the straight way...i mean in the present analysis the waveform is slightly deviated to upward. means in a slopped form.. if the transient time is appropriate does the waveform will be correct..? please help..