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