Sample and hold circuit tester

[Lutgeyara]

Hello
I am rying to creat a sample and hold tester using veriloga code. But i am confused hoe to develop this using timer? Here is some details of the code but i confused how to develop this. I am new in this section.

module Sh_tester (sh_inp, sample, avdd, in1, in2);

input in1, in2;
output sh_inp, sample, AVDD;
electrical sh_inp, sample,AVDD, in1, in2;

parameter real avdd_value = 5.0;
parameter real period = 100n; //sampling period
parameter real A = 1.0;
parameter real time_tol = 10p; //call for timer every 10p
parameter real td = 0.0; //delay from sampling to output
parameter real trf = 1n ;
parameter real tpd = 0;


real ts, var1, var2;

//file identifier

integer fid;

analog begin
    @(initial_step) begin
        fid = $fopen ("~/cdc/ece595/results/sample_hold_tester.pdf");
    //    f = 1/period  ;
    end
// close file
    @(initial_step) begin
        $fclose (fid);
    end

@ (timer(0, period, time_tol)) begin
        var1 = 0;





// supply voltages
    V(AVDD) <+ avdd_value ;

endmodule