Problem with the level 2 M file S function

I wrote the lvl 2 M file which consists of the If Elseif loop. and my i/p to the S function block is two sine wave blocks. Below is the logic which I used...

function Update(block)

vsd = block.InputPort(1).Data;
vsq = block.InputPort(2).Data;
  %k = block.Dwork(1).Data;
  %x = block.Dwork(2).Data;

if vsd>0 & vsq>=0 & vsd>vsq;
      k=1;

    elseif vsd>0 & vsq>=0 & vsd<=vsq;
        k=2;

    elseif vsd<=0 & vsq>0;
        k=3;

    elseif vsd<0 & vsq<=0 & vsd<vsq;
        k=4;

    elseif vsd<0 & vsq<0 & vsd>=vsq;
        k=5;

    elseif vsd>=0 & vsq<0;
        k=6;
 end
    block.Dwork(1).Data = k;

%end function

Now the question is it gives me the desired o/p only for the smaller simulation times, as I increased the simulation times, I didn't get the o/p which I want. It's like this If Elseif loop is true only for the first one or two cycles of the sine waves only.

So can anyone help me??

[Kaustubha Govind]

Perhaps you should set breakpoints in your code to debug the issue? It's hard for us to tell without looking at your input signal.