`include "constants.vams"
`include "disciplines.vams"

module pi( clk0, clk90, clk180, clk270, clksyn, clkref, code0, code1, code2, code3, code ) ;

       output  clk0, clk90, clk180, clk270, code;
       input   clksyn, clkref ;
       input   code0, code1, code2, code3;

       voltage clk0, clk90, clk180, clk270, clksyn, clkref, code ;
       voltage code0, code1, code2, code3;


       parameter real vcc = 1 from (0:inf);
       //parameter real td  = 0 from [0:inf);
       //parameter real tr  = 1p from [0:inf);
       //parameter real tt  = 0  from [0:inf);
       parameter integer dir = 1  from [-1:+1] exclude 0;

       parameter real clkfreq = 6e9 from (0:inf);
       parameter real PI_step = 32;


       integer c0, c1, c2, c3;
       real    resolution;
       real    clkperiod ;
       integer validcode ;


       analog begin

               clkperiod = 1/clkfreq ;
               resolution = clkperiod/PI_step;


               @(cross(V(clksyn) - vcc/2 , dir)) begin
                       c0 = (V(code0)>vcc/2) ? 1:0;
                       c1 = (V(code1)>vcc/2) ? 1:0;
                       c2 = (V(code2)>vcc/2) ? 1:0;
                       c3 = (V(code3)>vcc/2) ? 1:0;

                       validcode = c0 + 2*c1 + 4*c2 + 8*c3 ;
               end

               V(clk0)   <+ absdelay(V(clkref), validcode*resolution);
               V(clk90)  <+ absdelay(V(clkref), validcode*resolution+clkperiod/4);
               V(clk180) <+ absdelay(V(clkref), validcode*resolution+clkperiod/2);
               V(clk270) <+ absdelay(V(clkref), validcode*resolution+3*clkperiod/4);
               V(code)   <+ validcode;
       end


endmodule


The above has no syntax error and it is able to run simulation.
However, if the input transition clkref & clksyn arrive at the same time, it produces error! How to solve this? add delay?

just tried out with other codes, it produced error

it does not work as well.
please help

it got error when simulating. It halted at the cross function.
I tried out other method without the clksyn but replacing with clkref. it is still the same

newic,

  Part II

  BTW found the clksyn problem.

  If code=0, then the simulation runs. If code is a non-zero value
than the simulation stops. If you look in the simulation log file, you
will see an error message to the effect that "the delay is greater than
the maximum delay of 0", see Geoffrey Coram's comment.

  If you set the maximum delay value for the absdelay function
to be greater than 0, then the simulation will run. Please see the
following code snippet

              maxdelayval = (PI_step/2)*clkperiod ;


              @( cross( V(clksyn) - vcc/2 , dir)) begin
                      c0 = (V(code0) > vcc/2) ? 1:0;
                      c1 = (V(code1) > vcc/2) ? 1:0;
                      c2 = (V(code2) > vcc/2) ? 1:0;
                      c3 = (V(code3) > vcc/2) ? 1:0;

                      validcode = c0 + 2*c1 + 4*c2 + 8*c3 ;
              end

           p0      =      absdelay(V(clkref), validcode*resolution, maxdelayval);
           p90      =      absdelay(V(clkref), validcode*resolution+clkperiod/4, maxdelayval);
           p180      =      absdelay(V(clkref), validcode*resolution+clkperiod/2, maxdelayval);
           p270      =      absdelay(V(clkref), validcode*resolution+3*clkperiod/4, maxdelayval);

So the issue is not the cross function, it is that you defined the
maximum delay as 0. As a result, for any non-zero delay, the
simulation terminates.

                                                       Best Regards,

                                                          Sheldon

thanks for the helpful

btw, what is the transition filter?
I should use transition function to implement the delay function for a pulse wave signal?

transition filter is transition()

-Ken