Question

Write a Huffman decoder in verilog that inputs a text file with testbench.

Answer 1

verilog module code

module huffman_decoder(

input clk,

input reset,

input start,

input [2:0] in,

output reg [3:0] out

);

// SIGNAL DECLARATIONS

localparam s0 = 3'd0;

localparam s1 = 3'd1;

localparam s2 = 3'd2;

localparam s3 = 3'd3;

localparam s4 = 3'd4;

localparam s5 = 3'd5;

localparam s6 = 3'd6;

localparam s7 = 3'd7;

reg [2:0] buffer;

// FSM SIGNALS

reg [2:0] ps, ns;

// PRESENT STATE LOGIC

always@(posedge clk, posedge reset)

begin

if(reset)

begin

ps <= s0;

end

else

begin

ps <= ns;

end

end

// NEXT STATE LOGIC

always@*

begin

ns = ps;

case(ps)

s0 : begin

if(start)

begin

buffer = in;

ns = s1;

end

else

begin

ns = s0;

end

end

s1 : begin

if(buffer[2] == 1'b0)

ns = s2;

else if(buffer[1] == 1'b1)

ns = s3;

else

ns = s0;

end

s2 : begin

if(buffer[1] == 1'b0)

ns = s4;

else if(buffer[1] == 1'b1)

ns = s5;

else

ns = s0;

end

s3 : begin

if(buffer[1] == 1'b0)

ns = s6;

else if(buffer[1] == 1'b1)

ns = s7;

else

ns = s0;

end

s4 : begin

if(buffer[0] == 1'b0)

begin

out = 4'b1010;

ns = s0;

end

else if(buffer[0] == 1'b1)

begin

out = 4'b1011;

ns = s0;

end

else

begin

ns = s0;

end

end

s5 : begin

if(buffer[0] == 1'b0)

begin

out = 4'b1100;

ns = s0;

end

else if(buffer[1] == 1'b1)

begin

out = 4'b1101;

ns = s0;

end

else

begin

ns = s0;

end

end

s6 : begin

if(buffer[0] == 1'b0)

begin

out = 4'b1110;

ns = s0;

end

else if(buffer[1] == 1'b1)

begin

out = 4'b1111;

ns = s0;

end

else

begin

ns = s0;

end

end

s7 : begin

if(buffer[0] == 1'b0)

begin

out = 4'b1000;

ns = s0;

end

end

default : begin

ns = s0;

end

endcase

end

endmodule

-------------------

verilog module test bench

module huffman_decoder_tb;

// Inputs

reg clk;

reg reset;

reg start;

reg [2:0] in;

// Outputs

//wire ready;

//wire done_tick;

wire [3:0] out;

// Instantiate the Unit Under Test (UUT)

huffman_decoder uut (

.clk(clk),

.reset(reset),

.start(start),

.in(in),

//.ready(ready),

//.done_tick(done_tick),

.out(out)

);

initial begin

// Initialize Inputs

clk = 0;

reset = 0;

start = 0;

in = 0;

// Wait 100 ns for global reset to finish

#100;

  

// Add stimulus here

end

always #100 clk = ~clk;

initial begin

#1000 reset = 1'b1;

#1000 reset = 1'b0;

#1000 start = 1'b1;

#1000 in = 3'b000;

#1000 in = 3'b001;

#1000 in = 3'b010;

#1000 in = 3'b011;

#1000 in = 3'b100;

#1000 in = 3'b101;

#1000 in = 3'b110;

end

  

endmodule

Example Considered in Code

Character Huffman Code Decoded Output

A 000 1010

B 001 1011

C 010 1100

D 011 1101

E 100 1110

F 101 1111

0 110 1000