tests/asicworld/code_hdl_models_GrayCounter.v

   1 //==========================================
   2 // Function : Code Gray counter.
   3 // Coder    : Alex Claros F.
   4 // Date     : 15/May/2005.
   5 //=======================================
   6
   7 module GrayCounter
   8    #(parameter   COUNTER_WIDTH = 4)
   9
  10     (output reg  [COUNTER_WIDTH-1:0]    GrayCount_out,  //'Gray' code count output.
  11
  12      input wire                         Enable_in,  //Count enable.
  13      input wire                         Clear_in,   //Count reset.
  14
  15      input wire                         Clk);
  16
  17     /////////Internal connections & variables///////
  18     reg    [COUNTER_WIDTH-1:0]         BinaryCount;
  19
  20     /////////Code///////////////////////
  21
  22     always @ (posedge Clk)
  23         if (Clear_in) begin
  24             BinaryCount   <= {COUNTER_WIDTH{1'b 0}} + 1;  //Gray count begins @ '1' with
  25             GrayCount_out <= {COUNTER_WIDTH{1'b 0}};      // first 'Enable_in'.
  26         end
  27         else if (Enable_in) begin
  28             BinaryCount   <= BinaryCount + 1;
  29             GrayCount_out <= {BinaryCount[COUNTER_WIDTH-1],
  30                               BinaryCount[COUNTER_WIDTH-2:0] ^ BinaryCount[COUNTER_WIDTH-1:1]};
  31         end
  32
  33 endmodule