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////  Tubo 8051 cores common library Module                       ////

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////  This file is part of the Turbo 8051 cores project           ////

////  http://www.opencores.org/cores/turbo8051/                   ////

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////  Description                                                 ////

////  Turbo 8051 definitions.                                     ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

////  Author(s):                                                  ////

////      - Dinesh Annayya, dinesha@opencores.org                 ////

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//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source is distributed in the hope that it will be       ////

//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////

//// PURPOSE.  See the GNU Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

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// -----------------------------------------------------------------------

// Module Name      : stat_counter.v

// Company          : 

// Creation date    : 

// -----------------------------------------------------------------------

// Description      : This is the general purpose statistics counter. 

//                 

//                    

// References       : 

// ------------------------------------------------------------------------

//----------------- compiler directives -----------------------------------

// ------------------------------------------------------------------------

module stat_counter

  (

   // Clock and Reset Signals

   sys_clk,

   s_reset_n,

   count_inc,

   count_dec,

   reg_sel,

   reg_wr_data,

   reg_wr,

   cntr_intr,

   cntrout

   );

parameter CWD    = 1; // Counter Width

   //-------------------- Parameters -------------------------------------

   // ------------------- Clock and Reset Signals ------------------------

   input                     sys_clk;

   input                     s_reset_n;

   input                     count_inc; // Counter Increment

   input                     count_dec; // counter decrement, assuption does not under flow

   input                     reg_sel;

   input                     reg_wr;

   input  [CWD-1:0]          reg_wr_data;

   output                    cntr_intr;

   output [CWD-1:0]          cntrout;

   // ------------------- Register Declarations --------------------------

   reg [CWD-1:0]             reg_trig_cntr;

// ------------------- Logic Starts Here ----------------------------------

always @ (posedge sys_clk or negedge s_reset_n)

begin

   if (s_reset_n == 1'b0) begin

      reg_trig_cntr <= 'b0;

   end

   else begin

      if (reg_sel && reg_wr) begin

         reg_trig_cntr <= reg_wr_data;

      end

      else begin

         if (count_inc && count_dec)

            reg_trig_cntr <= reg_trig_cntr;

         else if (count_inc)

              reg_trig_cntr <= reg_trig_cntr + 1'b1;

         else if (count_dec)

              reg_trig_cntr <= reg_trig_cntr - 1'b1;

         else

            reg_trig_cntr <= reg_trig_cntr;

      end

   end

end

// only increment overflow is assumed  

// decrement underflow is not handled 

assign cntr_intr = ((reg_trig_cntr + 1) == 'h0 && count_inc) ;

assign cntrout = reg_trig_cntr;

endmodule // must_stat_counter