Aim : To write a program in verilog to implement digital code converters (binary to

gray,gray to binary and BCD to gray).

Description :

Digital code converters are used to convert digital code from one format to another.The code may be in

binary,gray,BCD format.We only represent numbers from (0-9) in binary into BCD code and it will be

simply their binary representation.While in case of gray code,MSB of binary code of any decimal number is

kept same and on moving to right bit is added with its previous bit (or doing xor operation).In this case carry

is neglected and the resulting sequence is known as gray code for an decimal number.

Gray code is a binary numeral system where two successive values differ in only one bit.

Code for (binary to gray) code conversion :

module bin_gry(B, G);

input [3:0] B;

output [3:0] G;

reg [3:0]G;

always@(B)

begin

case(B)

4'h0:G=4'h0;

4'h1:G=4'h1;

4'h2:G=4'h3;

4'h3:G=4'h2;

4'h4:G=4'h6;

4'h5:G=4'h7;

4'h6:G=4'h5;

4'h7:G=4'h4;

4'h8:G=4'hC;

4'h9:G=4'hD;

4'hA:G=4'hF;

4'hB:G=4'hE;

4'hC:G=4'hA;

4'hD:G=4'hB;

4'hE:G=4'h9;

4'hF:G=4'h8;

endcase

end

endmodule

Test fixture code:

module bin_gyr_txt_v;

// Inputs

reg [3:0] B;

// Outputs

wire [3:0] G;

// Instantiate the Unit Under Test (UUT)

bin_gry uut (

.B(B),

.G(G)

);

initial begin

// Initialize Inputs

B=4'h0;

#60;

B=4'h1;

#60;

B=4'h2;

#60;

B=4'h3;

#60;

B=4'h4;

#60;

B=4'h5;

#60;

B=4'h6;

#60;

B=4'h7;

#60;

B=4'h8;

#60;

B=4'h9;

#60; // TIME DELAY

B=4'hA;

#60;

B=4'hB;

#60;

B=4'hC;

#60;

B=4'hD;

#60;

B=4'hE;

#60;

B=4'hF;

#60;

$stop;

// Add stimulus here

end

endmodule

RTL Schematic for (binary to gray) code conversion :

Simulation Result for ( binary to gray) code conversion :

Code for (gray to binary) code conversion :

module gray_binary(g, b);

input [3:0] g;

output [3:0] b;

reg [3:0]b;

always@(g)

begin

b[3]=g[3];

b[2]=b[3]^g[2];

b[1]=b[2]^g[1];

b[0]=b[1]^g[0];

end

endmodule

RTL Schematic for (gray to binary) code conversion :

Simulation Result for (gray to binary) code conversion :

Code for (BCD to gray) code conversion :

module bcd_gry(BCD, G);

input [3:0] BCD;

output [3:0] G;

reg [3:0]G;

always@(BCD)

begin

G[3]=BCD[3];

G[2]=BCD[3]^BCD[2];

G[1]=BCD[2]^BCD[1];

G[0]=BCD[1]^BCD[0];

end

endmodule

Test fixture code:

initial begin

BCD=4'b0000;

#100;

BCD=4'b0001;

#100;

BCD=4'b0010;

#100;

BCD=4'b0011;

#100;

BCD=4'b0100;

#100;

BCD=4'b0101;

#100;

BCD=4'b0110;

#100;

BCD=4'b01110;

#100;

BCD=4'b1000;

#100;

BCD=4'b1001;

#100;

$stop;

end

Simulation Result for (BCD to gray) code conversion :