function [sys,x0,str,ts] = MSSFUNQConvert(t,x,u,flag)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 主要功能：根據輸入參數flag的數值調用相應的函數
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
switch flag
    case 0,
        %調用mdlInitializeSizes函數執行初始化
        [sys,x0,str,ts]=mdlInitializeSizes;
    case 2,
        %調用mdlUpdate函數計算離散狀態的數值
        sys=mdlUpdate(t,x,u);
    case 3,
        %調用mdlOutputs函數計算輸出信號的數值
        sys=mdlOutputs(t,x,u);
    case {1,4,9}
        %沒有相應的操作（沒有連續狀態）
        sys=[];
    otherwise
        error(['Unhandled flag=',num2str(flag)]);
end
%end MS_SFUN_QConvert



%=======================================================================
% mdlInitializeSizes
% Return the sizes, initial conditions, and sample times for the S-function.
%=======================================================================
%
function [sys,x0,str,ts] = mdlInitializeSizes
%調用simsizes獲得一個用于存放長度信息的結構
sizes = simsizes;
%設置連續狀態的個數
sizes.NumContStates  = 0;
%設置兩個離散狀態
sizes.NumDiscStates  =2;
%設置輸出信號的個數為1
sizes.NumOutputs     =1;
%設置輸入信號的個數為1
sizes.NumInputs      = 1;
%設置直接反饋的狀態，0表示沒有直接反饋，1表示存在直接反饋
sizes.DirFeedthrough = 1;
%設置抽樣時間的個數（大于等于1）
sizes.NumSampleTimes = 1;
%通過simsizes把sizes結構返回給sys
sys = simsizes(sizes);

%設置S函數的初始狀態x0
x0  = [0 0]';
%設置S函數的保留參數str(應該設置為空向量
str = [];
%初始化抽樣時間
ts  = [-1 0]; 

% end mdlInitializeSizes

%
%=======================================================================
% mdlUpdate
% Handle discrete state updates, sample time hits, and major time step
% requirements.
%=======================================================================
%
function sys = mdlUpdate(t,x,u)
%就算S函數的離散狀態并且通過sys參數返回給Simulink
if x(1)==0
    x(2)=-1*u;
    x(1)=1;
else
    x(1)=0;
end
sys=x;


%end mdlUpdate

%
%=======================================================================
% mdlOutputs
% Return the output vector for the S-function
%=======================================================================
%
function sys = mdlOutputs(t,x,u)
%就算S函數的輸出信號并且通過sys參數返回給Simulink
if x(1)==0
    sys=u;
else
    sys=x(2);
end



%end mdlOutputs