function [sys,x0,str,ts] = MSSFUNQConvert(t,x,u,flag)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 主要功能：根據(jù)輸入?yún)?shù)flag的數(shù)值調(diào)用相應(yīng)的函數(shù)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
switch flag
    case 0,
        %調(diào)用mdlInitializeSizes函數(shù)執(zhí)行初始化
        [sys,x0,str,ts]=mdlInitializeSizes;
    case 2,
        %調(diào)用mdlUpdate函數(shù)計(jì)算離散狀態(tài)的數(shù)值
        sys=mdlUpdate(t,x,u);
    case 3,
        %調(diào)用mdlOutputs函數(shù)計(jì)算輸出信號(hào)的數(shù)值
        sys=mdlOutputs(t,x,u);
    case {1,4,9}
        %沒(méi)有相應(yīng)的操作（沒(méi)有連續(xù)狀態(tài)）
        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(diào)用simsizes獲得一個(gè)用于存放長(zhǎng)度信息的結(jié)構(gòu)
sizes = simsizes;
%設(shè)置連續(xù)狀態(tài)的個(gè)數(shù)
sizes.NumContStates  = 0;
%設(shè)置兩個(gè)離散狀態(tài)
sizes.NumDiscStates  =2;
%設(shè)置輸出信號(hào)的個(gè)數(shù)為1
sizes.NumOutputs     =1;
%設(shè)置輸入信號(hào)的個(gè)數(shù)為1
sizes.NumInputs      = 1;
%設(shè)置直接反饋的狀態(tài)，0表示沒(méi)有直接反饋，1表示存在直接反饋
sizes.DirFeedthrough = 1;
%設(shè)置抽樣時(shí)間的個(gè)數(shù)（大于等于1）
sizes.NumSampleTimes = 1;
%通過(guò)simsizes把sizes結(jié)構(gòu)返回給sys
sys = simsizes(sizes);

%設(shè)置S函數(shù)的初始狀態(tài)x0
x0  = [0 0]';
%設(shè)置S函數(shù)的保留參數(shù)str(應(yīng)該設(shè)置為空向量
str = [];
%初始化抽樣時(shí)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(shù)的離散狀態(tài)并且通過(guò)sys參數(shù)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(shù)的輸出信號(hào)并且通過(guò)sys參數(shù)返回給Simulink
if x(1)==0
    sys=u;
else
    sys=x(2);
end



%end mdlOutputs