Answer to Question #230415 in Software Engineering for Asjad

Question

Design an 8-bit carry save array multiplier using Verilog HDL. Simulate it with 4 test cases. Prepare a .PDF by including the Verilog codes along with the screen shots of the simulation outputs. Attach the .PDF.

Answer 1

8-bit Verilog Code for Booth’s Multiplier

module multiplier(prod, busy, mc, mp, clk, start);

output [15:0] prod;

output busy;

input [7:0] mc, mp;

input clk, start;

reg [7:0] A, Q, M;

reg Q_1;

reg [3:0] count;

wire [7:0] sum, difference;

always @(posedge clk)

begin

if (start) begin

A <= 8'b0;

M <= mc;

Q <= mp;

Q_1 <= 1'b0;

count <= 4'b0;

end

else begin

case ({Q[0], Q_1})

2'b0_1 : {A, Q, Q_1} <= {sum[7], sum, Q};

2'b1_0 : {A, Q, Q_1} <= {difference[7], difference, Q};

default: {A, Q, Q_1} <= {A[7], A, Q};

endcase

count <= count + 1'b1;

end

end

alu adder (sum, A, M, 1'b0);

alu subtracter (difference, A, ~M, 1'b1);

assign prod = {A, Q};

assign busy = (count < 8);

endmodule

//The following is an alu.

//It is an adder, but capable of subtraction:

//Recall that subtraction means adding the two's complement--

//a - b = a + (-b) = a + (inverted b + 1)

//The 1 will be coming in as cin (carry-in)

module alu(out, a, b, cin);

output [7:0] out;

input [7:0] a;

input [7:0] b;

input cin;

assign out = a + b + cin;

endmodule

Testbench for Booth’s Multiplier

module testbench;

reg clk, start;

reg [7:0] a, b;

wire [15:0] ab;

wire busy;

multiplier multiplier1(ab, busy, a, b, clk, start);

initial begin

clk = 0;

$display("first example: a = 3 b = 17");

a = 3; b = 17; start = 1; #50 start = 0;

#80 $display("first example done");

$display("second example: a = 7 b = 7");

a = 7; b = 7; start = 1; #50 start = 0;

#80 $display("second example done");

$finish;

end

always #5 clk = !clk;

always @(posedge clk) $strobe("ab: %d busy: %d at time=%t", ab, busy,

$stime);

endmodule