From f1604e8736300c3ccfb7aeebd9fca3f059f18104 Mon Sep 17 00:00:00 2001
From: Konstantin Pavlov <pavlovconst@gmail.com>
Date: Tue, 25 Feb 2020 15:38:56 +0300
Subject: [PATCH] Added gray code converters

---
 bin2gray.sv |  34 +++++++++++++++
 gray2bin.sv |  37 +++++++++++++++++
 gray_tb.sv  | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 187 insertions(+)
 create mode 100644 bin2gray.sv
 create mode 100644 gray2bin.sv
 create mode 100644 gray_tb.sv

diff --git a/bin2gray.sv b/bin2gray.sv
new file mode 100644
index 0000000..f17e671
--- /dev/null
+++ b/bin2gray.sv
@@ -0,0 +1,34 @@
+//------------------------------------------------------------------------------
+// bin2gray.sv
+// Konstantin Pavlov, pavlovconst@gmail.com
+//------------------------------------------------------------------------------
+
+// INFO ------------------------------------------------------------------------
+//  Gray code to binary converter
+//  Combinational design
+
+
+/* --- INSTANTIATION TEMPLATE BEGIN ---
+
+bin2gray #(
+  .WIDTH( 32 )
+) BG1 (
+  .bin_in(  ),
+  .gray_out(  )
+);
+
+--- INSTANTIATION TEMPLATE END ---*/
+
+module bin2gray #( parameter
+  WIDTH = 32
+)(
+  input [WIDTH-1:0] bin_in,
+  output logic[WIDTH-1:0] gray_out
+);
+
+always_comb begin
+  gray_out[WIDTH-1:0] = bin_in[WIDTH-1:0]^(bin_in[WIDTH-1:0]>>1);
+end
+
+endmodule
+
diff --git a/gray2bin.sv b/gray2bin.sv
new file mode 100644
index 0000000..6c3fe4a
--- /dev/null
+++ b/gray2bin.sv
@@ -0,0 +1,37 @@
+//------------------------------------------------------------------------------
+// gray2bin.sv
+// Konstantin Pavlov, pavlovconst@gmail.com
+//------------------------------------------------------------------------------
+
+// INFO ------------------------------------------------------------------------
+//  Binary to gray code converter
+//  Combinational design
+
+
+/* --- INSTANTIATION TEMPLATE BEGIN ---
+
+gray2bin #(
+  .WIDTH( 32 )
+) GB1 (
+  .gray_in(  ),
+  .bin_out(  )
+);
+
+--- INSTANTIATION TEMPLATE END ---*/
+
+module gray2bin #( parameter
+   WIDTH = 32
+)(
+   input [WIDTH-1:0] gray_in,
+   output [WIDTH-1:0] bin_out
+);
+
+genvar i;
+generate
+   for( i=0; i<WIDTH; i++ ) begin
+      assign bin_out[i] = ^gray_in[WIDTH-1:i];
+   end
+endgenerate
+
+endmodule
+
diff --git a/gray_tb.sv b/gray_tb.sv
new file mode 100644
index 0000000..e406c33
--- /dev/null
+++ b/gray_tb.sv
@@ -0,0 +1,116 @@
+//------------------------------------------------------------------------------
+// gray_tb.sv
+// Konstantin Pavlov, pavlovconst@gmail.com
+//------------------------------------------------------------------------------
+
+// INFO ------------------------------------------------------------------------
+// testbench for bin2gray and gray2bin module
+
+
+`timescale 1ns / 1ps
+
+module gray_tb();
+
+logic clk200;
+initial begin
+  #0 clk200 = 1'b0;
+  forever
+    #2.5 clk200 = ~clk200;
+end
+
+logic rst;
+initial begin
+  #0 rst = 1'b0;
+  #10.2 rst = 1'b1;
+  #5 rst = 1'b0;
+  //#10000;
+  forever begin
+    #9985 rst = ~rst;
+    #5 rst = ~rst;
+  end
+end
+
+logic nrst;
+assign nrst = ~rst;
+
+logic rst_once;
+initial begin
+  #0 rst_once = 1'b0;
+  #10.2 rst_once = 1'b1;
+  #5 rst_once = 1'b0;
+end
+
+logic nrst_once;
+assign nrst_once = ~rst_once;
+
+logic [31:0] DerivedClocks;
+clk_divider #(
+  .WIDTH( 32 )
+) cd1 (
+  .clk( clk200 ),
+  .nrst( nrst_once ),
+  .ena( 1'b1 ),
+  .out( DerivedClocks[31:0] )
+);
+
+logic [31:0] E_DerivedClocks;
+edge_detect ed1[31:0] (
+  .clk( {32{clk200}} ),
+  .nrst( {32{nrst_once}} ),
+  .in( DerivedClocks[31:0] ),
+  .rising( E_DerivedClocks[31:0] ),
+  .falling(  ),
+  .both(  )
+);
+
+logic [15:0] RandomNumber1;
+c_rand rng1 (
+  .clk( clk200 ),
+  .rst( rst_once ),
+  .reseed( 1'b0 ),
+  .seed_val( DerivedClocks[31:0] ),
+  .out( RandomNumber1[15:0] )
+);
+
+logic start;
+initial begin
+  #0 start = 1'b0;
+  #100 start = 1'b1;
+  #20 start = 1'b0;
+end
+
+// Module under test ==========================================================
+
+`define WIDTH 32
+
+logic [`WIDTH-1:0] bin = 0;
+
+always_ff @(posedge clk200) begin
+  if(~nrst_once) begin
+    bin[`WIDTH-1:0] <= 0;
+  end else begin
+    bin[`WIDTH-1:0] <= bin[`WIDTH-1:0] + 1'b1;
+  end
+end
+
+logic [`WIDTH-1:0] gray;
+bin2gray #(
+  .WIDTH( `WIDTH )
+) BG1 (
+  .bin_in( bin[`WIDTH-1:0] ),
+  .gray_out( gray[`WIDTH-1:0] )
+);
+
+logic [`WIDTH-1:0] bin2;
+gray2bin #(
+  .WIDTH( `WIDTH )
+) GB1 (
+  .gray_in( gray[`WIDTH-1:0] ),
+  .bin_out( bin2[`WIDTH-1:0] )
+);
+
+//assert property
+//  (bin[`WIDTH-1:0] == bin2[`WIDTH-1:0])
+//else $error("It's gone wrong");
+
+endmodule