function [sys,x0,str,ts] = s_function(t,x,u,flag)
global counter in_put w step out_put hs_size hs L r;
switch flag,
case 0,
    [sys,x0,str,ts]=mdlInitializeSizes;
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case 1,
     sys=0;
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 case 3,
     step=u(2);
     counter=counter+1;
     in_put=[u(1);in_put(1:(hs_size-1))];
     x=in_put'*hs;
     r=[x;r(1:(L-1))];
     w=w-step*u(3)*r;
     sys=w'*r;
    
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
case { 2, 4, 9 },
    sys = [];
otherwise
    error(['Unhandled flag = ',num2str(flag)]);
end
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function [sys,x0,str,ts]=mdlInitializeSizes
global counter in_put w step out_put hs_size hs L r;
L=300;           %表示濾波器的長度
in_put=zeros(hs_size,1);
out_put=zeros(L,1);
w=zeros(L,1);         %L表示濾波器的權系數
r=zeros(L,1);


hs_size=8;       %次級聲道的傳遞函數長度
hs=[0.9321 0.6500 -0.2000 0.3900 0.6277 0.4140 0.1040 -0.1000]' %次級通道數學模型
%hs=zeros((hs_size-1),1);hs=[hs;1];  %次級通道數學模型


sizes = simsizes;
sizes.NumContStates  = 0;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 1;
sizes.NumInputs      = 3;
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 1;   % at least one sample time is needed
sys = simsizes(sizes);
x0  = [];
str = [];
ts  = [0 0];