function [sys,x0,str,ts] = m05_lisanxitong(t,x,u,flag)
%定義離散系統(tǒng)的S函數(shù)例子 
%此S函數(shù)遵循下面的方程： 
%    x(n+1) = Ax(n) + Bu(n)
%    y(n)   = Cx(n) + Du(n)
%   
%   See sfuntmpl.m for a general S-function template.
%
% 生成離散線性系統(tǒng)
A=[-1   -0.05
    1     0];
B=[1     -6
   0     -2];
C=[ 0    2
    1    0];
D=[-2    0
    2     0];

switch flag,

  %%%%%%%%%%%%%%%%%%
  % Initialization ——初始化%
  %%%%%%%%%%%%%%%%%%
  case 0,
    [sys,x0,str,ts] = mdlInitializeSizes(A,B,C,D);

  %%%%%%%%%%
  % Update ——提升離散狀態(tài)%
  %%%%%%%%%%
  case 2,                                                
    sys = mdlUpdate(t,x,u,A,B,C,D); 

  %%%%%%%%%%
  % Output ———計算輸出%
  %%%%%%%%%%
  case 3,                                                
    sys = mdlOutputs(t,x,u,A,C,D);

  %%%%%%%%%%%%%
  % Terminate ——終止%
  %%%%%%%%%%%%%
  case 9,                                                
    sys = []; % do nothing

  %%%%%%%%%%%%%%%%%%%%
  % Unexpected flags——無用標示 %
  %%%%%%%%%%%%%%%%%%%%
  otherwise
    error(['unhandled flag = ',num2str(flag)]);
end

%end m05_lisanxitong    自定義子函數(shù)結(jié)束

%以下是各子函數(shù)模塊
%=======================================================================
% mdlInitializeSizes——初始化子函數(shù)
% Return the sizes, initial conditions, and sample times for the S-function.
%=======================================================================
%
function [sys,x0,str,ts] = mdlInitializeSizes(A,B,C,D)   

sizes = simsizes;
sizes.NumContStates  = 0;
sizes.NumDiscStates  = size(A,1);
sizes.NumOutputs     = size(D,1);
sizes.NumInputs      = size(D,2);
sizes.DirFeedthrough = 1;
sizes.NumSampleTimes = 1;

sys = simsizes(sizes);

x0  = ones(sizes.NumDiscStates,1);
str = [];
ts  = [1 0]; 

% end mdlInitializeSizes

%
%===============================================================
% mdlUpdate————提升離散狀態(tài)子函數(shù)
% Handle discrete state updates, sample time hits, and major time step
% requirements.
%===============================================================
%
function sys = mdlUpdate(t,x,u,A,B,C,D)

sys = A*x+B*u;

%end mdlUpdate

%
%===============================================================
% mdlOutputs ———計算輸出子函數(shù)
% Return the output vector for the S-function
%===============================================================
%
function sys = mdlOutputs(t,x,u,A,C,D)

sys = C*x+D*u;

%end mdlOutputs