--***************************************************************
--* File         : UB2BCD.vhd                                   *
--* Created      : 2008/01/20 Osamu Kawashima                   *
--* Modified     : Time-stamp: <08/01/22 05:40:00 kawasan>      *
--*                                                             *
--* 8bit-Data -> 3-BCD                                          *
--*                                                             *
--* Copyright 2008 Osamu Kawashima. all rights reserved         *
--***************************************************************

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity UB2BCD is
	port (
		RESET           : in    std_logic;
		SYSCLK          : in    std_logic;
		BIN_I           : in    std_logic_vector(7 downto 0);
		START           : in    std_logic;

		STOP            : out   std_logic;
		BCD_O           : out   std_logic_vector(11 downto 0)
	);
end UB2BCD;

architecture RTL of UB2BCD is

	constant ZERO32         : std_logic_vector(31 downto 0) := (others=>'0');

	type STATE is (S_READY, S_CORRECTION, S_SHIFT, S_CMPEND);
	signal current_state    : STATE;
	signal next_state       : STATE;
	--constant S_READY        : std_logic_vector := x"0";
	--constant S_CORRECTION   : std_logic_vector := x"1";
	--constant S_SHIFT        : std_logic_vector := x"2";
	--constant S_CMPEND       : std_logic_vector := x"3";
	--signal current_state    : std_logic_vector(S_READY'range);
	--signal next_state       : std_logic_vector(S_READY'range);

	signal bin_code         : std_logic_vector(7 downto 0);
	signal bcd_code         : std_logic_vector(11 downto 0);
	signal bcd_code_o       : std_logic_vector(bcd_code'left downto 0);
	signal bcd_correction   : std_logic_vector(bcd_code'left downto 0);
	signal bcd_o_is         : std_logic_vector(bcd_code'left downto 0);
	signal loop_cnt         : std_logic_vector(3 downto 0);
	signal cmpend           : std_logic;
	signal stop_is          : std_logic;

begin

	-- State-Machine --
	process (RESET,SYSCLK)
	begin
		if RESET='1' then
			current_state <= S_READY;
		elsif SYSCLK'event and SYSCLK='1' then
			current_state <= next_state;
		end if;
	end process;

	process (current_state,START,cmpend)
	begin
		if current_state=S_READY then
			if START='1' then
				next_state <= S_CORRECTION;
			else
				next_state <= S_READY;
			end if;
		elsif current_state=S_CORRECTION then
			next_state <= S_SHIFT;
		elsif current_state=S_SHIFT then
			next_state <= S_CMPEND;
		elsif current_state=S_CMPEND then
			if cmpend='1' then
				next_state <= S_READY;
			else
				next_state <= S_CORRECTION;
			end if;
		else
			next_state <= S_READY;
		end if;
	end process;
	-- State-Machine --

	process (RESET,SYSCLK)
	begin
		if RESET='1' then
			loop_cnt <= x"0";
		elsif SYSCLK'event and SYSCLK='1' then
			if current_state=S_READY and START='1' then
				loop_cnt <= x"8";
			elsif current_state=S_SHIFT then
				loop_cnt <= loop_cnt - 1;
			else
				loop_cnt <= loop_cnt;
			end if;
		end if;
	end process;

	cmpend <= '1' when loop_cnt=x"0" else '0';

	process (RESET,SYSCLK)
	begin
		if RESET='1' then
			bin_code <= (others=>'0');
			bcd_code <= (others=>'0');
		elsif SYSCLK'event and SYSCLK='1' then
			if current_state=S_READY and START='1' then
				bin_code <= BIN_I;
				bcd_code <= (others=>'0');
			elsif current_state=S_SHIFT then
				bin_code <= bin_code(bin_code'left-1 downto 0) & '0';
				bcd_code <= bcd_correction(bcd_correction'left-1 downto 0) & bin_code(bin_code'left);
			else
				bin_code <= bin_code;
				bcd_code <= bcd_code;
			end if;
		end if;
	end process;

	bcd_code_o(3 downto 0) <= bcd_code(3 downto 0) + x"3";
	bcd_code_o(7 downto 4) <= bcd_code(7 downto 4) + x"3";
	bcd_code_o(11 downto 8) <= bcd_code(11 downto 8) + x"3";

	bcd_correction(3 downto 0) <= bcd_code_o(3 downto 0) when bcd_code_o(3)='1' else bcd_code(3 downto 0);
	bcd_correction(7 downto 4) <= bcd_code_o(7 downto 4) when bcd_code_o(7)='1' else bcd_code(7 downto 4);
	bcd_correction(11 downto 8) <= bcd_code_o(11 downto 8) when bcd_code_o(11)='1' else bcd_code(11 downto 8);

	process (RESET,SYSCLK)
	begin
		if RESET='1' then
			loop_cnt <= x"0";
		elsif SYSCLK'event and SYSCLK='1' then
			if current_state=S_READY and START='1' then
				loop_cnt <= x"8";
			elsif current_state=S_SHIFT then
				loop_cnt <= loop_cnt - 1;
			else
				loop_cnt <= loop_cnt;
			end if;
		end if;
	end process;

	process (RESET,SYSCLK)
	begin
		if RESET='1' then
			bcd_o_is <= (others=>'0');
		elsif SYSCLK'event and SYSCLK='1' then
			if current_state=S_CMPEND and cmpend='1' then
				bcd_o_is <= bcd_code;
			else
				bcd_o_is <= bcd_o_is;
			end if;
		end if;
	end process;

	BCD_O <= bcd_o_is;

	process (RESET,SYSCLK)
	begin
		if RESET='1' then
			stop_is <= '1';
		elsif SYSCLK'event and SYSCLK='1' then
			if current_state=S_READY and START='1' then
				stop_is <= '0';
			elsif cmpend='1' then
				stop_is <= '1';
			else
				stop_is <= stop_is;
			end if;
		end if;
	end process;

	STOP <= stop_is;

end RTL;