Question

Design a Verilog code for 64x64 array multiplier. Use behavioral Verilog description with full adders and/or half adders. Please include testbench

Answer 1

module array_multiplier(a, b, y);

parameter width = 8;
input [width-1:0] a, b;
output [width-1:0] y;

wire [width*width-1:0] partials;

genvar i;
assign partials[width-1 : 0] = a[0] ? b : 0;
generate for (i = 1; i < width; i = i+1) begin:gen
    assign partials[width*(i+1)-1 : width*i] = (a[i] ? b << i : 0) +
                                   partials[width*i-1 : width*(i-1)];
end endgenerate

assign y = partials[width*width-1 : width*(width-1)];

endmodule

Test bench for above program


module array_multiplier_tb;

reg [31:0] a, b;
wire [31:0] y;

array_multiplier #(
        .width(32)
) uut (
        .a(a),
        .b(b),
        .y(y)
); 

reg [31:0] xrnd = 1;
task xorshift32;
begin
        xrnd = xrnd ^ (xrnd << 13);
        xrnd = xrnd ^ (xrnd >> 17);
        xrnd = xrnd ^ (xrnd <<  5);
end endtask

integer i;
initial begin
        // $dumpfile("array_multiplier_tb.vcd");
        // $dumpvars(0, array_multiplier_tb);

        for (i = 0; i < 100; i = i+1)
        begin
                #10;

                xorshift32;
                a <= xrnd;
                xorshift32;
                b <= xrnd;

                #10;

                $display("%d * %d = %d (%d)", a, b, y, a*b);
                if (y != a*b) begin
                        $display("ERROR!");
                        $finish;
                end
        end
        $display("PASSED.");
end

endmodule