--------------------------------------------------------------------------
--------------------------------------------------------------------------
--	File Name 	: elevator_control.v
--	Author(s)	: Jay(anta) Roy
--	Affiliation	: Laboratory for Digital Design Environments
--			  Department of Electrical & Computer Engineering
--			  University of Cincinnati
--	Date Created	: Sept 1990.
--	Introduction	: Behavioral description of the Elevator Controller
--			  written in a synthesizable subset of VHDL.
--	Source		: ISPS description from 
--                        L. J. Hafer and A. C. Parker,
--			  ``Automated Synthesis of Digital Hardware'',
-- 			  IEEE Tran. Computers, Feb 1982.
--
--	Disclaimer	: This comes with absolutely no guarantees of any
--			  kind (just stating the obvious ...)
--
--      Acknowledgement : The Distributed Synthesis Systems research at 
--                        the Laboratory for Digital Design Environments,
--                        University of Cincinnati, is sponsored in part 
--                        by the Defense Advanced Research Projects Agency 
--                        under order number 7056 monitored by the Federal 
--                        Bureau of Investigation under contract number 
--                        J-FBI-89-094.
--
--------------------------------------------------------------------------
--------------------------------------------------------------------------
package types is
  type BIT_ARRAY_15 is array (0 to 15) of BIT;
  -- type floor_range is range 0 to 8;
end types;

use Work.types.all;
use Work.functions.all;

entity elevator_control is
   port ( car_floor : in INTEGER;
	  up_call, down_call, button : in BIT;
	  car_call : out BIT_ARRAY_15
   );
end elevator_control;

architecture behavior of elevator_control is
-- signal scan_floor : int_Wired_OR INTEGER := 0;
   signal scan_floor : INTEGER := 7;

begin
  process
  begin
--   scan_floor <= 0 after 2 ns;
--   wait on scan_floor until scan_floor = 8;
     if (scan_floor = 7) then
	scan_floor <= 0 ;
     else
	scan_floor <= scan_floor + 1 ;
     end if;
     wait on scan_floor;
  end process ;

  process
     variable index : INTEGER := 0;
  begin
     wait on scan_floor;
     if up_call='1' then
	index := 7 + scan_floor;
	car_call(index) <= '1';
     end if;
     if down_call='1' then
	car_call(scan_floor) <= '1';
     end if;
     if button='1' then
	if car_floor > scan_floor then
	  car_call(scan_floor) <= '1';
	else
	  index := 7 + scan_floor;
	  car_call(index) <= '1';
	end if;
     end if;
--   wait on scan_floor;
--   wait for 1 ns;
--   scan_floor <= scan_floor + 1;
--   if scan_floor = 8 then
--     wait on scan_floor until scan_floor = 0;
--   end if;
  end process;
end behavior;