In this example, we verify a simple single port RAM. Of course in real life we really don't get to verify a memory model.

As usual our testbench will look as shown in figure below.

So the verification components are split into following blocks

• Base Object
• Transaction Generator
• Driver
• Input Monitor
• Output Monitor
• Scoreboard
• SV testbench top
• Ports File
• HDL Testbench top

 1 `ifndef MEM_BASE_OBJECT_SV
 2 `define MEM_BASE_OBJECT_SV
 3 class mem_base_object;
 4   bit [7:0] addr;
 5   bit [7:0] data;
 6   // Read = 0, Write = 1
 7   bit rd_wr;
 8 endclass
 9 `endif

  1 `ifndef MEM_TXGEN_SV
  2 `define MEM_TXGEN_SV
  3 class mem_txgen;
  4   mem_base_object  mem_object;
  5   mem_driver  mem_driver;
  6   
  7   integer num_cmds;
  8 
  9 function new(virtual mem_ports ports);
 10   begin
 11     num_cmds = 3;
 12     mem_driver = new(ports);
 13   end
 14 endfunction
 15 
 16 
 17 task gen_cmds();
 18   begin
 19     integer i = 0;
 20     for (i=0; i < num_cmds; i ++ ) begin
 21       mem_object = new();
 22       mem_object.addr = $random();
 23       mem_object.data = $random();
 24       mem_object.rd_wr = 1;
 25       mem_driver.drive_mem(mem_object);
 26       mem_object.rd_wr = 0;
 27       mem_driver.drive_mem(mem_object);
 28     end
 29   end
 30 endtask
 31 
 32 endclass
 33 `endif

  1 `ifndef MEM_DRIVER_SV
  2 `define MEM_DRIVER_SV
  3 
  4 class mem_driver;
  5   virtual mem_ports ports;
  6 
  7 function new(virtual mem_ports ports);
  8   begin
  9     this.ports = ports;
 10     ports.address    = 0;
 11     ports.chip_en    = 0;
 12     ports.read_write = 0;
 13     ports.data_in    = 0;
 14   end
 15 endfunction
 16 
 17 task drive_mem (mem_base_object object);
 18   begin
 19     @ (posedge ports.clock);
 20     ports.address    = object.addr;
 21     ports.chip_en    = 1;
 22     ports.read_write = object.rd_wr;
 23     ports.data_in    = (object.rd_wr) ? object.data : 0;
 24     if (object.rd_wr) begin
 25       $display("Driver : Memory write access-> Address : %x Data : %x\n", 
 26         object.addr,object.data);
 27     end else begin
 28       $display("Driver : Memory read  access-> Address : %x\n", 
 29         object.addr);
 30     end
 31     @ (posedge ports.clock);
 32     ports.address    = 0;
 33     ports.chip_en    = 0;
 34     ports.read_write = 0;
 35     ports.data_in    = 0;
 36  end
 37 endtask
 38 
 39 endclass
 40 `endif
 41 

  1 `ifndef MEM_IP_MONITOR_SV
  2 `define MEM_IP_MONITOR_SV
  3 class mem_ip_monitor;
  4   mem_base_object mem_object;
  5   mem_scoreboard  sb;
  6   virtual mem_ports       ports;
  7 
  8 function new (mem_scoreboard sb,virtual mem_ports ports);
  9   begin  
 10     this.sb    = sb;
 11     this.ports = ports;
 12   end
 13 endfunction
 14 
 15 
 16 task input_monitor();
 17   begin
 18     while (1) begin
 19       @ (posedge ports.clock);
 20       if ((ports.chip_en == 1) && (ports.read_write == 1)) begin
 21          mem_object = new();
 22          $display("input_monitor : Memory wr access-> Address : %x Data : %x", 
 23             ports.address,ports.data_in);
 24 	 mem_object.addr = ports.address;
 25 	 mem_object.data = ports.data_in;
 26          sb.post_input(mem_object);
 27       end
 28     end
 29   end
 30 endtask
 31 
 32 endclass
 33 
 34 `endif

  1 `ifndef MEM_OP_MONITOR_SV
  2 `define MEM_OP_MONITOR_SV
  3 
  4 class mem_op_monitor;
  5   mem_base_object mem_object;
  6   mem_scoreboard sb;
  7   virtual mem_ports       ports;
  8 
  9 function new (mem_scoreboard sb,virtual mem_ports ports);
 10   begin
 11     this.sb    = sb;
 12     this.ports = ports;
 13   end
 14 endfunction
 15   
 16 
 17 task output_monitor();
 18   begin
 19     while (1) begin
 20       @ (negedge ports.clock);
 21       if ((ports.chip_en == 1) && (ports.read_write == 0)) begin
 22         mem_object = new();
 23         $display("Output_monitor : Memory rd access-> Address : %x Data : %x", 
 24           ports.address,ports.data_out);
 25         mem_object.addr = ports.address;
 26         mem_object.data = ports.data_out;
 27         sb.post_output(mem_object);
 28       end
 29     end
 30   end
 31 endtask
 32 
 33 
 34 endclass
 35 
 36 `endif

  1 `ifndef MEM_SCOREBOARD_SV
  2 `define MEM_SCOREBOARD_SV
  3 
  4 class mem_scoreboard;
  5   // Create a keyed list to store the written data
  6   // Key to the list is address of write access
  7   mem_base_object mem_object [*];
  8 
  9   // post_input method is used for storing write data
 10   // at write address
 11 task post_input (mem_base_object  input_object);
 12   begin
 13     mem_object[input_object.addr] = input_object;
 14   end
 15 endtask
 16   // post_output method is used by the output monitor to 
 17   // compare the output of memory with expected data
 18 task post_output (mem_base_object  output_object);
 19   begin
 20    // Check if address exists in scoreboard  
 21    if (mem_object[output_object.addr]  ! = null) begin 
 22       mem_base_object  in_mem = mem_object[output_object.addr];
 23       $display("scoreboard : Found Address %x in list",output_object.addr);
 24       if (output_object.data  ! = in_mem.data)  begin
 25         $display ("Scoreboard : Error : Exp data and Got data don't match");
 26         $display("             Expected -> %x",
 27           in_mem.data);
 28         $display("             Got      -> %x",
 29           output_object.data);
 30       end else begin
 31         $display("Scoreboard : Exp data and Got data match");
 32       end
 33    end 
 34   end 
 35 endtask
 36 
 37 endclass
 38 
 39 `endif

Copyright © 1998-2014

Deepak Kumar Tala - All rights reserved

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