trigwksp.m

数字通信第四版原书的例程

function [sys,x0] = trigwksp(t,x,u,flag,num_pulse,yin,...
                       init_out, init_state, threshold, ini)
%TRIGWKSP reads a data or a character from workspace by counting the
%         number of triggers. Different from the time driven from
%         workspace block, this is a event driven block.
%         YIN: data to be read in. block output size is the column of
%              this block. The block outputs a row of the data each
%              time. The data is 

%       Wes Wang
%       Copyright (c) 1995-96 by The MathWorks, Inc.

if flag == 2 				%refresh states
  sys = x;
  sys(2) = u;
  % the state will be changed only under the following condition
  if (x(2) <= threshold) & (u > threshold)
    if sys(3) == 0
      xlength = length(x);
      resid = 5:length(x);
      %refresh the output
      sys(1) = sys(1) + 1;
      if sys(1) <= sys(4)
	if isstr(yin)
	  sys(resid) = abs(yin(sys(1),:));
	else
	  sys(resid) = yin(sys(1),:);
	end;
      else
	sys(resid) = 0 * sys(resid);
      end;
    end;
    sys(3) = rem(sys(3)+1, num_pulse);
  elseif (t <= 0)
    if (length(x)-4) == length(ini)
      sys(5:length(x)) = ini(:);
    elseif ~isempty(ini)
      sys(5:length(x)) = ones(length(x)-4, 1)*ini;      
    end      
  end;
elseif flag == 3 			%output calculation
  sys = x(5:length(x));
elseif flag == 0 			%initial condition
  [n,m]=size(yin);
  if isempty(n) | isempty(m)
    n=0;
    m=0;
    [x,y]=get_param;
    x = [x '/' y];
    disp(['There is nothing in the triggered workspace block ',x]);
  end;
  sys = [0;4+m;m;1;0;0];
  if isempty(init_state)
    init_state = 0; 
  end;
  if isempty(init_out)
    init_out = zeros(1,m);   
  elseif length(init_out ~= m)
    init_out = ones(1,m) * init_out(1);
  else
    tmp=zeros(1,m);
    tmp(:) = init_out(:);
  end;
  x0 = [0,init_state,0,n,init_out];
  % x0 = [position_in_yin, last_input_value, pulse_number_counting,...
  % size_of_yin, output_value]
else 					%all of the other cases.
  sys = [];
  % if flag == 4, sys = []; means this block has to be called at 
  % every time-hit
end;