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-- Copyright (C) 2002 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs is free software; you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the
-- Free Software Foundation; either version 2 of the License, or (at
-- your option) any later version.
-- VESTs is distributed in the hope that it will be useful, but WITHOUT
-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-- FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
-- for more details.
-- You should have received a copy of the GNU General Public License
-- along with VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
entity scheduler is
end entity scheduler;
architecture test of scheduler is
constant scheduling_delay : delay_length := 5 ns;
subtype request_type is natural range 0 to 20;
type server_status_type is (ready, busy);
signal first_priority_request,
first_normal_request,
reset_request : request_type := 0;
signal functional_request, equivalent_request : request_type;
signal priority_waiting : boolean := false;
signal server_status : server_status_type := busy;
begin
functional_scheduler : block is
port ( request : out request_type );
port map ( request => functional_request );
begin
-- code from book
scheduler :
request <= first_priority_request after scheduling_delay
when priority_waiting and server_status = ready else
first_normal_request after scheduling_delay
when not priority_waiting and server_status = ready else
unaffected
when server_status = busy else
reset_request after scheduling_delay;
-- end code from book
end block functional_scheduler;
--------------------------------------------------
equivalent_scheduler : block is
port ( request : out request_type );
port map ( request => equivalent_request );
begin
-- code from book
scheduler : process is
begin
if priority_waiting and server_status = ready then
request <= first_priority_request after scheduling_delay;
elsif not priority_waiting and server_status = ready then
request <= first_normal_request after scheduling_delay;
elsif server_status = busy then
null;
else
request <= reset_request after scheduling_delay;
end if;
wait on first_priority_request, priority_waiting, server_status,
first_normal_request, reset_request;
end process scheduler;
-- end code from book
end block equivalent_scheduler;
--------------------------------------------------
stimulus : process is
begin
first_priority_request <= 10; wait for 20 ns;
first_normal_request <= 5; wait for 20 ns;
server_status <= ready; wait for 20 ns;
server_status <= busy; wait for 20 ns;
priority_waiting <= true; wait for 20 ns;
server_status <= ready; wait for 20 ns;
first_normal_request <= 7; wait for 20 ns;
first_priority_request <= 12; wait for 20 ns;
wait;
end process stimulus;
verifier :
assert functional_request = equivalent_request
report "Functional and equivalent models give different results";
end architecture test;
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