function structure =  SS_eqn(name,Bond_number,Bonds,Direction,cr,args, ...
    structure,filenum);

disp("SS_eqn");
name,Bond_number,Bonds,Direction

% 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
global local_y_index
global at_top_level

			
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% Version control history
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% $Id$
% %% $Log$
% %% Revision 1.21  1998/07/28 14:21:31  peterg
% %% Vector SS ports.
% %%
% %% Revision 1.20  1998/07/08 14:42:52  peterg
% %% Removed the annoying info message - it causes problems with big
% %% systems
% %%
% %% Revision 1.19  1998/07/08 11:33:54  peterg
% %% Replace mtt_info by mtt_error when appropriate
% %%

  
n_bonds = length(Bond_number)	# Multi port?
for i=1:n_bonds			# Loop over all the bonds
  bond_number = Bond_number(i);
  bonds = Bonds(i,:);
  direction = Direction(i,:);
  
 Named_Port = name(1)=="[";	

 if Named_Port
   sname = name(2:length(name)); #Strip the []
 else
   sname = name;
 end;
  
   if Named_Port&&~at_top_level % It's a named port
    % Effort 
    if bonds(1,1)==-1 % Source
      local_u_index = local_u_index + 1
      fprintf(filenum, "%s := %s_MTTu%d;\n", ...
              varname(sname, bond_number,1), sname, local_u_index);
    else % Sensor
      local_y_index = local_y_index + 1

    end;  
  else				# 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(sname, bond_number,1),inputs);
      else % Sensor
	outputs = outputs+1;
	fprintf(filenum, "MTTy(%d,1) := %s;\n", ...
		outputs, varname(sname, bond_number,1));
      end;
    elseif strcmp(effort_attribute, "unknown") % Unknown input
      unknown_inputs = unknown_inputs + 1;
      fprintf(filenum, "%s := MTTUi%d;\n", ...
	      varname(sname, 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(sname, 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(sname, 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(sname, bond_number,-1),inputs);
      else % Sensor
	outputs = outputs+1;
	fprintf(filenum, "MTTy(%d,1) := %s;\n", outputs, ...
		varname(sname, bond_number,-1));
      end;
    elseif strcmp(flow_attribute, "unknown") % Unknown input
      unknown_inputs = unknown_inputs + 1;
      fprintf(filenum, "%s := MTTUi%d;\n", ...
	      varname(sname, 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(sname, 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(sname, bond_number,-1));
	else
	  mtt_error([flow_attribute, " not appropriate for an output "]);
	end;
      end;
    end;
  end;
  structure(3) = inputs;
  structure(4) = outputs;
  structure(5) = zero_outputs;
  structure(6) = unknown_inputs;
  
end;