Subversion Repositories scalable_arbiter

/*
 * Copyright (c) 2008, Kendall Correll
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
`timescale 1ns / 1ps
 
// This bench simply applies the vectors in the pattern file,
// and tests that the output matches the expected values. This
// test is usful to verify basic behavior, but it is difficult
// to generate vectors for large configurations.
 
`define WIDTH 8
`define SELECT_WIDTH 8
`define TURNAROUND 3
//`define TURNAROUND 6 for arbiter x2
`define TICK 10
`define HALF_TICK 5
`define TEST_VEC_COUNT 241
`define TEST_VEC_MULT 2
`define PATTERN_FILE "tb_arbiter.txt"
 
module tb_arbiter;
 
reg reset;
reg clock;
 
reg [`WIDTH-1:0] req;
wire [`WIDTH-1:0] grant;
wire [`SELECT_WIDTH-1:0] select;
wire valid;
 
reg [`WIDTH-1:0] pattern[(`TEST_VEC_MULT*`TEST_VEC_COUNT)-1:0];
reg [`WIDTH-1:0] grant_expected;
 
integer test_i;
integer grant_i;
integer grant_count;
integer failures;
integer monitor_exceptions;
 
//
// UUT
//
 
arbiter #(
	.width(`WIDTH),
	.select_width(`SELECT_WIDTH)
) arbiter (
	.enable(1'b1),
	.req(req),
	.grant(grant),
	.select(select),
	.valid(valid),
 
	.clock(clock),
	.reset(reset)
);
 
//
// clock
//
 
always @(clock)
	#`HALF_TICK clock <= !clock;
 
//
// test monitors
//
 
always @(grant)
begin
	grant_count = 0;
	for(grant_i = 0; grant_i < `WIDTH; grant_i = grant_i + 1)
	begin
		if(grant[grant_i])
		begin
			grant_count = grant_count + 1;
 
			if(!req[grant_i])
			begin
				monitor_exceptions = monitor_exceptions + 1;
 
				$display("EXCEPTION @%e: grant line %d with no req",
					$realtime, grant_i);
			end
 
			if(select != grant_i)
			begin
				monitor_exceptions = monitor_exceptions + 1;
 
				$display("EXCEPTION @%e: select of %d does not match grant of line %d",
					$realtime, select, grant_i);
			end
		end
	end
 
	if(grant_count > 1)
	begin
		monitor_exceptions = monitor_exceptions + 1;
 
		$display("EXCEPTION @%e: grant %h asserts multiple lines",
			$realtime, grant);
	end
end
 
//
// test sequence
//
 
initial
begin
	$readmemb(`PATTERN_FILE, pattern);
	failures = 0;
	monitor_exceptions = 0;
 
	clock = 1;
	req = 0;
	reset = 1;
	#`TICK @(negedge clock) reset = 0;
 
	// apply reqs, and test grants against exepcted values
	for(test_i = 0; test_i < `TEST_VEC_COUNT; test_i = test_i + 1)
	begin
		#`TICK;
 
		req = pattern[test_i*`TEST_VEC_MULT];
		grant_expected = pattern[test_i*`TEST_VEC_MULT + 1];
 
		#(`TURNAROUND*`TICK);
 
		if(grant != grant_expected)
		begin
			failures = failures + 1;
 
			$display("FAILED %d: req %h, grant %h (expected %h)",
				test_i, req, grant, grant_expected);
		end
		else
		begin
			$display("ok %d: req %h, grant %h (expected %h)",
				test_i, req, grant, grant_expected);
		end
	end
 
	$display("%d failures", failures);
	$display("%d monitor exceptions", monitor_exceptions);
 
	if(failures == 0 && monitor_exceptions == 0)
		$display("PASS");
	else
		$display("FAIL");
end
 
endmodule