// VerilogA for Testing, DNLpart, veriloga

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

//enSYS@gmx.com

module DNLpart (vclk,vin,d0,d1,d2,d3,d4,d5,d6,d7);
input d0,d1,d2,d3,d4,d5,d6,d7;
input vclk,vin;
electrical d0,d1,d2,d3,d4,d5,d6,d7;
electrical vin,vclk;

parameter real vtrans_clk = 0.5; // Threshold
parameter real fullscale = 1.0; // For Gain Error Estimation
parameter integer maxcode = 128; // Number of bins
parameter integer method = 0;


real X[7:0];
real Y[7:0];
real dnl[7:0];
real inl[7:0];
integer maxcount,count,i;
real measbin,offseterr,gainerr,dnlmax,dnlmin,inlmax,inlmin;
integer dnlout,inlout;
real S,S1,S2,S3,S4,P,P1,P0,A1,A0;

analog begin
@(initial_step)
    begin
        for(i=0;i<1023;i=i+1)begin
                X[i] = 0;
                Y[i] = 0;
                dnl[i] = 0;
                inl[i] = 0;
            end
        count = 0;
        dnlout = $fopen("~/dnlmeasure.dat");
        inlout = $fopen("~/inlmeasure.dat");
    end
@(cross(V(vclk) - vtrans_clk, 0))begin
        X[count] = $abstime;
        Y[count] = V(vin);
        count = count + 1;
    end
@(final_step)begin
        maxcount = count;
        // Linear Approximation (Best Fit)
        S1 = 0; S2 = 0; S3 = 0; S4 = 0;
        for (i=0;i<maxcount;i=i+1)begin
                S1 = S1 + pow(X[i],2);
                S2 = S2 + X[i];
                S3 = S3 + X[i]*Y[i];
                S4 = S4 + Y[i];
            end
        P = S1*maxcount - pow(S2,2);
        P1 = S3*maxcount - S2*S4;
        P0 = S1*S4 - S2*S3;
        A1 = P1/P;
        A0 = P0/P;
        // LSB Estimation
        for (i=1;i<maxcount;i=i+1)begin
                S = S + (Y[i] - Y[i-1]);
            end
        measbin = S/(maxcount - 1);
        // Offset, Gain Error Estimation
        offseterr = -A0/measbin;
        gainerr = (fullscale - maxcode*measbin)/measbin;
        // DNL, INL estimation
        dnlmax = 0; dnlmin = 0; inlmax = 0; inlmin = 0;
        for (i=0;i<=maxcount;i=i+1)// DNL
        if (i == 0 || i == maxcount) dnl[i] = 0;
        else dnl[i] = (Y[i]-Y[i-1])/measbin-1.0;
        if (method == 0) begin
        // End points INL
        if (i == 0) inl[i] = 0;
        else inl[i] = inl[i-1]+dnl[i];
        end else begin
                // Best fit INL
                if (i == maxcount) inl[i] = 0;
                else inl[i] = ((measbin*(i+1.0/2.0)+A0) - Y[i])/measbin;
            end
// Summary
if (dnl[i]>dnlmax) dnlmax = dnl[i];
if (dnl[i]<dnlmin) dnlmin = dnl[i];
if (inl[i]>inlmax) inlmax = inl[i];
if (inl[i]<inlmin) inlmin = inl[i];
// Write for drawing
$fdisplay(dnlout,"%d\t%10.6f",i,dnl[i]);
$fdisplay(inlout,"%d\t%10.6f",i,inl[i]);
end
$fclose(dnlout);
$fclose(inlout);
// Summaries
$display("Summmary of ADC Static Parameters");
$display("Measure Module:\t%m");
$display("Number of Codes:\t%d",maxcount+1);
$display("Max Offset Error:\t%+.2f",offseterr);
$display("Max Gain Error:\t\t%+.2f",gainerr);
$display("Max DNL:\t\t%+.2f/%+.2f",dnlmin,dnlmax);
$display("Max INL:\t\t%+.2f/%+.2f",inlmin,inlmax);
$display("Plot dnlmeasure.dat & inlmeasure.dat for details...");
end
endmodule