function structure =  SS_eqn(name,bond_number,bonds,direction,cr,args, ...
    structure,filenum);

% Set up globals to count the component inputs and outputs. This relies on
% the named SS (the ports) being in the correct order. Using globals here
% avoids changing the common argument list for all _eqn files for something
% which is only used for named SS components.
global local_u_index

			
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% Version control history
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% $Id$
% %% $Log$




% %% Revision 1.19  1998/07/08 11:33:54  peterg
% %% Replace mtt_info by mtt_error when appropriate
% %%
% %% Revision 1.18  1998/07/08 11:30:45  peterg
% %% Removed second (fileID) argument from mtt_info
% %%
% %% Revision 1.17  1998/07/04 07:15:44  peterg

  effort_attribute = 'external';
end;

if strcmp(flow_attribute,'')
  flow_attribute = 'external';
end;


inputs = structure(3);
outputs = structure(4);
zero_outputs = structure(5);
unknown_inputs = structure(6);






% Is it a named port? (Name begins with [)
Named_Port = (name(1)=='[');

if Named_Port
  % Strip the [
  name = name(2:length(name));
end;

if Named_Port&&~at_top_level % It's a named port

% Note: we don't have numbered ports now, so the correct indices are deduced
% by incrementing the two globals: local_u_index and local_y_index
% $$$   % Convert string to number
% $$$   % port_number = abs(flow_attribute)-abs('0');
% $$$   % port_number = str2num(flow_attribute);

% $$$   %Compute port number
% $$$   str_port_number = flow_attribute;
% $$$   N_string = length(str_port_number);
% $$$   port_number=0;
% $$$   for i=1:N_string
% $$$     port_number = 10*port_number + abs(str_port_number(i))-abs('0');
% $$$   end;

  % Effort 
  if bonds(1,1)==-1 % Source
    local_u_index = local_u_index + 1;
    fprintf(filenum, '%s := %s_MTTu%d;\n', ...
        varname(name, bond_number,1), name, local_u_index);
  else % Sensor
    local_y_index = local_y_index + 1;
    fprintf(filenum, '%s_MTTy%d := %s;\n', ...
        name, local_y_index, varname(name, bond_number,1));
  end;
  % Flow 
  if bonds(1,2)==1 % Source
    local_u_index = local_u_index + 1;




    fprintf(filenum, '%s := %s_MTTu%d;\n', ...
        varname(name, bond_number,-1), name, local_u_index);
  else % Sensor
    local_y_index = local_y_index + 1;
    fprintf(filenum, '%s_MTTy%d := %s;\n', ...
        name, local_y_index, varname(name, bond_number,-1));
  end;  
  return
end;

% Now do SS which are not ports.
% Effort
if strcmp(effort_attribute, 'external')
  if bonds(1,1)==-1 % Source
    inputs = inputs+1;
    fprintf(filenum, '%s := MTTu(%d,1);\n', ...
	varname(name, bond_number,1),inputs);
  else % Sensor
    outputs = outputs+1;





    fprintf(filenum, 'MTTy(%d,1) := %s;\n', ...
	outputs, varname(name, bond_number,1));
  end;
elseif strcmp(effort_attribute, 'unknown') % Unknown input
  unknown_inputs = unknown_inputs + 1;
  fprintf(filenum, '%s := MTTUi%d;\n', ...
      varname(name, bond_number,1), unknown_inputs);
elseif strcmp(effort_attribute, 'internal')
  % Do nothing
else 
  if bonds(1,1)==-1 % Named or unknown source
    fprintf(filenum, '%s := %s;\n', ...
	varname(name, bond_number,1), effort_attribute);
  else % Sensor
    if strcmp(effort_attribute, 'zero') %Zero output
      zero_outputs = zero_outputs + 1;
      fprintf(filenum, 'MTTyz%d := %s;\n', ...
	  zero_outputs, varname(name, bond_number,1));
    else
      mtt_error([effort_attribute, ' not appropriate for an output ']);
    end;
  end;
end;
  
% Flow
if strcmp(flow_attribute, 'external')
  if bonds(1,2)==1 % Source
    inputs = inputs+1;
    fprintf(filenum, '%s := MTTu(%d,1);\n', varname(name, bond_number,-1),inputs);
  else % Sensor
    outputs = outputs+1;
    fprintf(filenum, 'MTTy(%d,1) := %s;\n', outputs, ...
	varname(name, bond_number,-1));
  end;
elseif strcmp(flow_attribute, 'unknown') % Unknown input
  unknown_inputs = unknown_inputs + 1;
  fprintf(filenum, '%s := MTTUi%d;\n', ...
      varname(name, bond_number,-1), unknown_inputs);
elseif strcmp(flow_attribute, 'internal')
  % Do nothing
else % Named constant
  if bonds(1,2)==1 % Source
    fprintf(filenum, '%s := %s;\n', ...
	varname(name, bond_number,-1), flow_attribute);
  else % Sensor
    if strcmp(flow_attribute, 'zero') %Zero output
      zero_outputs = zero_outputs + 1;
      fprintf(filenum, 'MTTyz%d := %s;\n', ...
	  zero_outputs, varname(name, bond_number,-1));
    else
      mtt_error([flow_attribute, ' not appropriate for an output ']);
    end;
  end;
end;

structure(3) = inputs;
structure(4) = outputs;
structure(5) = zero_outputs;
structure(6) = unknown_inputs;