Generic Gray Code Counter

omara007 · Dec 12, 2006

aslijia said:
Added after 3 minutes:

omara007 said:

I don't want to have the glitches resulted from the binary counting

Click to expand...

if you use combination logic, you must have glitches, even the simplest combination circuit with only 2 ANDs, by some inputs.

Counters are not COMBINATIONAL circuits

echo47 · Dec 12, 2006

I whipped up this synchronous Gray counter without using any intermediate counter or tedious 'case' statement. The 'bin' value is combinatorial. The number of bits is easily adjusted.

Code:

module top (clk, gray);
  parameter             bits = 8;
  input                 clk;
  reg        [bits-1:0] bin = 0;
  output reg [bits-1:0] gray = 0;

  integer i;
  always @ (gray)
    for (i = 0; i < bits; i = i + 1)
      bin[i] <= ^(gray >> i);

  always @ (posedge clk)
    gray <= ((bin + 1'd1) >> 1) ^ (bin + 1'd1);  // to count down, change both + to -
endmodule

Generic Gray Code Counter

omara007

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echo47

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Generic Gray Code Counter

omara007

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