VerilogA $abstime limitation to 2pi

Create an analog function fmod like this (similar to the C function, but not part of the Verilog-A language):

analog function real fmod;
    input num,den;
    real num,den;
    fmod=num-floor(num/den)*den;
endfunction 

analog begin
  angle_in_rad = fmod((current_velocity*$abstime + phi),`M_TWO_PI);
  $strobe(angle_in_rad);
end

That will do what you want, I think. I'm not sure it's the $abstime you want to limit to 2 pi, but the angle_in_rad (I assume)?

Yes, You are right I want to limit the angle in rad to 2 pi, but the $abstime is always increasing,
But I did not get your answer fully, how can I create the analog function?

Yes, You are right I want to limit the angle in rad to 2 pi, but the $abstime is always increasing,
But I did not get your answer fully, how can I create the analog function?

Ajmal Hussian said:

But I did not get your answer fully, how can I create the analog function?

Include the function definition within your module - here's a complete (simple) made up example to show it in use:

//

`include "disciplines.vams"
`include "constants.vams"
module testfmod(sigout);
electrical sigout;
output sigout;

parameter real current_velocity=1e6;
parameter real phi=0.1;
real angle_in_rad;

analog function real fmod;
    input num,den;
    real num,den;
    fmod=num-floor(num/den)*den;
endfunction 

analog begin
  angle_in_rad = fmod((current_velocity*$abstime + phi),`M_TWO_PI);
  $strobe(angle_in_rad);
end

endmodule

I have tried both of the following ways and it works. But the problem is that during the tansition from 360 to 0 there is always an intermediate value at 180 degree which creates errors. Do you have any idea why it behaves like this?

I can't see a good reason why that would happen - I don't see that with my example above. There's a risk with your implementation that the argument to the function might increase by more than one cycle in one step and so it's not truly limiting it to the modulo - I don't see any benefit in your approach compared with mine (it only seems to have a disadvantage that it might go wrong at times). In either case though, I can't see why it would have a value at 180 degrees - unless the input stepped from just below 360 to 360+180 to 720. Perhaps getting your Verilog-A model to $strobe or $debug the input to the function before it's called (and the return value too).