always @(posedge Clock)
   if ( Processor.Datapath.PC == 99 )
      begin
         $display("Terminating at instruction 99\n");
         @(posedge Clock);
         @(posedge Clock);
         $stop;
         $finish;
      end

// finish after `sim_time if not already terminated at instruction 99
initial
   begin
      `ifdef sim_time
      `else
         `define sim_time 500us
      `endif
      #`sim_time
      $display("Too long - giving up");
      $stop;
      $finish;
   end

   // status interpretation

   function [7*8:1] get_state;
      input value;
      case (value)
         0	: get_state = "Execute";
         1	: get_state = "Fetch";
         default	: get_state = "*ERR*";
      endcase
   endfunction

   wire [7*8:1] State;
   assign State = get_state(Processor.Control.state);

   function [6*8:1] get_mnemonic;
      input [3:0] opcode;
      case (opcode)
         `NOP		: get_mnemonic = "NOP";
         `JMP		: get_mnemonic = "JMP";
         `JMPZ		: get_mnemonic = "JMPZ";
         `JMPNZ		: get_mnemonic = "JMPNZ";
         `LDA		: get_mnemonic = "LDA";
         `ADD		: get_mnemonic = "ADD";
         `SUB		: get_mnemonic = "SUB";
         `AND		: get_mnemonic = "AND";
         `OR		: get_mnemonic = "OR";
         `NOT		: get_mnemonic = "NOT";
         `LSL		: get_mnemonic = "LSL";
         `LSR		: get_mnemonic = "LSR";
         `STA		: get_mnemonic = "STA";
         default	: get_mnemonic = "*ERR*";
      endcase
   endfunction

   wire [6*8:1] Mnemonic;
   assign Mnemonic = get_mnemonic(Processor.Control.Opcode);

   function [6*8:1]  extract_mnemonic;
      input [15:0] instruction;
      extract_mnemonic = get_mnemonic(instruction[15:12]);
   endfunction

   function [5*8:1] get_alufunc;
      input [3:0] fncode;
      case (fncode)
         `FnACC		: get_alufunc = " A";
         `FnMem		: get_alufunc = " M";
         `FnADD		: get_alufunc = " A+M";
         `FnSUB		: get_alufunc = " A-M";
         `FnAND		: get_alufunc = " A&M";
         `FnOR		: get_alufunc = " A|M";
         `FnNOT		: get_alufunc = " ~A";
         `FnLSL		: get_alufunc = " A<<1";
         `FnLSR		: get_alufunc = " A>>1";
         default	: get_alufunc = "*ERR*";
      endcase
   endfunction

   wire [5*8:1] ALU_Function;
   assign ALU_Function = get_alufunc(Processor.Datapath.Function);

   function [11:0] get_operand;
      input [15:0] instruction;
      get_operand = instruction[11:0];
   endfunction

   function [9*8:1] get_zero;
      input flag;
      case (flag)
         0	: get_zero = "ACC<>Zero";
         1	: get_zero = "ACC==Zero";
         default	: get_zero = "*ERR*";
      endcase
   endfunction

   wire [9*8:1] Zero_String;
   assign Zero_String = get_zero(Processor.Zflag);

   function [5*8:1] get_wnr;
      input signal;
      case (signal)
         0	: get_wnr = "read";
         1	: get_wnr = "write";
         default	: get_wnr = "*ERR*";
      endcase
   endfunction

   wire [5*8:1] Memory_Operation;
   assign Memory_Operation = get_wnr(Processor.Mem_Write);

   function [1*8:1] get_digit_zero;
      input [15:0] number;
      get_digit_zero = "0" + (number%10);
   endfunction
   function [1*8:1] get_digit;
      input [15:0] number;
      if ( number > 0 )
        get_digit = get_digit_zero(number);
      else
        get_digit = " ";
   endfunction

   function [10*8:1] disassemble;
      input [15:0] instruction;
      disassemble = {
        get_mnemonic(instruction[15:12]),
        get_digit(instruction[11:0]/1000),
        get_digit(instruction[11:0]/100),
        get_digit(instruction[11:0]/10),
        get_digit_zero(instruction[11:0])
      };
   endfunction

   wire [10*8:1] InstructionText;
   assign InstructionText = disassemble(Processor.Datapath.IR);


   reg [10*8:1] DisassemblyListing [ 255:0 ];
   integer i;
   initial
      begin
         #1ns for ( i = 0; i < 256; i = i + 1 )
	   DisassemblyListing[i] = disassemble(Processor.Memory.Data_stored[i]);
      end