//------------------------------------------------------------------------------
//
// tb_lowlevel_subtractor32.v
// -----------------------------------------------------------------------------
// Testbench for 32-bit subtractor.
//
// Authors: Pavel Shatov
//
// Copyright (c) 2015-2016, NORDUnet A/S
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// - Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// - Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// - Neither the name of the NORDUnet nor the names of its contributors may be
// used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
//------------------------------------------------------------------------------
//------------------------------------------------------------------------------
`timescale 1ns / 1ps
//------------------------------------------------------------------------------
module tb_lowlevel_subtractor32;
//
// Inputs
//
reg clk;
reg [31: 0] a;
reg [31: 0] b;
reg b_in;
//
// Outputs
//
wire [31: 0] d;
wire b_out;
//
// Test Vectors {a, b, b_in}
//
wire [64: 0] vec_0 = {32'h00000000, 32'h00000000, 1'b0}; // all zeroes, no borrow
wire [64: 0] vec_1 = {32'h00000000, 32'h00000000, 1'b1}; // all zeroes with borrow
wire [64: 0] vec_2 = {32'h00000000, 32'hFFFFFFFF, 1'b0}; // zeroes and ones, no borrow
wire [64: 0] vec_3 = {32'h00000000, 32'hFFFFFFFF, 1'b1}; // zeroes and ones with borrow
wire [64: 0] vec_4 = {32'hFFFFFFFF, 32'h00000000, 1'b0}; // ones and zeroes, no borrow
wire [64: 0] vec_5 = {32'hFFFFFFFF, 32'h00000000, 1'b1}; // ones and zeroes with borrow
wire [64: 0] vec_6 = {32'hFFFFFFFF, 32'hFFFFFFFF, 1'b0}; // all ones, no borrow
wire [64: 0] vec_7 = {32'hFFFFFFFF, 32'hFFFFFFFF, 1'b1}; // all ones with borrow
wire [64: 0] vec_8 = {32'hd898c296, 32'h37bf51f5, 1'b0}; // random values, no borrow
wire [64: 0] vec_9 = {32'hf4a13945, 32'hcbb64068, 1'b0}; // random values, no borrow
wire [64: 0] vec_10 = {32'h2deb33a0, 32'h6b315ece, 1'b0}; // random values, no borrow
wire [64: 0] vec_11 = {32'h77037d81, 32'h2bce3357, 1'b0}; // random values, no borrow
wire [64: 0] vec_12 = {32'h63a440f2, 32'h7c0f9e16, 1'b1}; // random values with borrow
wire [64: 0] vec_13 = {32'hf8bce6e5, 32'h8ee7eb4a, 1'b1}; // random values with borrow
wire [64: 0] vec_14 = {32'he12c4247, 32'hfe1a7f9b, 1'b1}; // random values with borrow
wire [64: 0] vec_15 = {32'h6b17d1f2, 32'h4fe342e2, 1'b1}; // random values with borrow
//
// UUT
//
subtractor32_wrapper uut
(
.clk (clk),
.a (a),
.b (b),
.d (d),
.b_in (b_in),
.b_out (b_out)
);
//
// Testbench Routine
//
reg ok = 1;
initial begin
//
clk = 0;
//
#100;
//
test_subtractor32(vec_0);
test_subtractor32(vec_1);
test_subtractor32(vec_2);
test_subtractor32(vec_3);
test_subtractor32(vec_4);
test_subtractor32(vec_5);
test_subtractor32(vec_6);
test_subtractor32(vec_7);
//
test_subtractor32(vec_8);
test_subtractor32(vec_9);
test_subtractor32(vec_10);
test_subtractor32(vec_11);
test_subtractor32(vec_12);
test_subtractor32(vec_13);
test_subtractor32(vec_14);
test_subtractor32(vec_15);
//
if (ok) $display("tb_lowlevel_subtractor32: SUCCESS");
else $display("tb_lowlevel_subtractor32: FAILURE");
//
$finish;
//
end
//
// Test Routine
//
reg [31: 0] dd; // reference value of difference
reg bb; // reference value of borrow
reg dd_ok; // result matches reference value
task test_subtractor32;
input [64: 0] vec;
begin
/* break down test vector */
a = vec[64:33];
b = vec[32: 1];
b_in = vec[ 0: 0];
/* calculate reference values */
{bb, dd} = {1'b0, a} - {1'b0, b} - {32'd0, b_in};
/* send one clock tick */
#10 clk = 1;
#10 clk = 0;
/* check outputs */
dd_ok = (d == dd) && (b_out == bb);
/* display results */
$display("test_subtractor32(): 0x%08X - (0x%08X + %01d) = {%01d, 0x%08X} [%0s]", a, b, b_in, b_out, d, dd_ok ? "OK" : "ERROR");
/* update global flag */
ok = ok && dd_ok;
end
endtask
endmodule
//------------------------------------------------------------------------------
// End-of-File
//------------------------------------------------------------------------------
