function [sys,x0,str,ts]=sfun_mseries(t,x,u,flag)

switch flag,
    case 0,
       [sys,x0,str,ts]=mdlInitializeSizes;
    case 3,
        sys=mdlOutputs(t,x,u);
    case{2,4,9}
        sys=[];
    otherwise
        error(['Unhandled flag = ',num2str(flag)]);
end

function[sys,x0,str,ts]=mdlInitializeSizes
sizes = simsizes;
sizes.NumContStates  = 0;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 1;
sizes.NumInputs      = 0;
sizes.DirFeedthrough = 0;
sizes.NumSampleTimes = 1;   
sys = simsizes(sizes);
x0  = [];
str = [];                 
ts = [1 0]; 

function sys=mdlOutputs(t,x,u)
sys=2*randint-1;