--/*DIV．VHD*/--串行BCD碼除法模塊
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;


entity div is
    Port (clk,rst:in std_logic;
	 		 bei,chu:in std_logic_vector(31 downto 0);
			 shang:out std_logic_vector(31 downto 0);
			 dian:out integer range -10 to 10 );
end div;

architecture Behavioral of div is
type ss is array (1 to 8) of std_logic_vector(3 downto 0);
signal s:ss;
signal a,b:std_logic_vector(31 downto 0);
signal n:integer range -10 to 10;
signal c:integer range 0 to 8;
signal k:integer range 1 to 7;
signal d:integer range 0 to 1;

begin
process(clk,k,n,c,s,bei,chu,a,b,rst)
variable cnt:integer range 0 to 31;
variable m:std_logic_vector(3 downto 0);

begin
	if rst='0' then
	k<=5;n<=7;c<=8;cnt:=0;m:="0000";s<=(("0000"),("0000"),("0000"),("0000"),("0000"),("0000"),("0000"),("0000"));
		shang<=(others=>'0');
	elsif rising_edge(clk) then
	case k is
		when 1=>if b(31 downto 28)=0 then 
						b<=b(27 downto 0)&"0000";
						if n<10 then
							n<=n+1;
						else
							k<=5;
							n<=7;
						end if;
					else
						k<=2;
					end if;
		when 2=>if a<b then 
						b<="0000"&b(31 downto 4);
						n<=n-1;
					else
						if n=0 then
							k<=5;
							n<=7;
						else
							k<=3;
						end if;
					end if;
		when 3=>	if a(cnt+3 downto cnt)>=b(cnt+3 downto cnt)+d then 
						a(cnt+3 downto cnt)<=a(cnt+3 downto cnt)-b(cnt+3 downto cnt)-d;
						d<=0;
					else
						a(cnt+3 downto cnt)<=a(cnt+3 downto cnt)+10-b(cnt+03 downto cnt)-d;
						d<=1;
					end if;
					if cnt<28 then
						cnt:=cnt+4;
						k<=3;
					else
						k<=4;
					end if;
		when 4=> m:=m+1;
					cnt:=0;
					d<=0;
					if a<=b then 
						s(c)<=m;
						m:="0000";
						if c=1 then 
							k<=5;
						else
							k<=7;
							c<=c-1;
							if a(31 downto 28)=0 then
								a<=a(27 downto 0)&"0000";
							else
								b<="0000"&b(31 downto 4);
							end if;
						end if;
					else
						k<=3;
					end if;
		when 7=>if a>=b then
						k<=3;
					else
						a<=a(27 downto 0)&"0000";
						s(c)<=m;
						if c>=2 then
							c<=c-1;
						else
							k<=5;
						end if;
					end if;
		when 5=>a<=bei;
				  b<=chu;
				  shang<=s(8)&s(7)&s(6)&s(5)&s(4)&s(3)&s(2)&s(1);
				  k<=6;
				  dian<=n;
				  n<=7;
				  m:="0000";
				  c<=8;
				  cnt:=0;
		when 6=>if a(31 downto 28)=0 then
						a<=a(27 downto 0)&"0000";
						if n>=0 then 
							n<=n-1;
						else
							n<=7;
							k<=5;
						end if;
					else
						k<=1;
					end if;
						
		when others=>k<=5;
		end case;
		end if;
end process;	
end Behavioral;