--将最大数为511的9位二进制数转成3位BCD
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY BCD IS
PORT(LOAD : IN STD_LOGIC;
CLK : IN STD_LOGIC;
DATA : IN STD_LOGIC_VECTOR(8 DOWNTO 0);
BCD_SEG : OUT STD_LOGIC_VECTOR(11 DOWNTO 0));
END BCD;
ARCHITECTURE GO OF BCD IS
SIGNAL C : STD_LOGIC_VECTOR(11 DOWNTO 0);
SIGNAL A : STD_LOGIC_VECTOR(8 DOWNTO 0);
SIGNAL K : STD_LOGIC;
TYPE STS IS (S0,S1,S2,S3,S4,S5,S6);
SIGNAL ST : STS;
BEGIN
PROCESS(CLK)
VARIABLE T : INTEGER RANGE 0 TO 15;
BEGIN
IF CLK'EVENT AND CLK='1' THEN
IF LOAD='0' THEN
T:=0;
C<=X"000";
A<=DATA;
ST<=S1;
K<='0';
ELSE
CASE ST IS
WHEN S0=>
K<=A(8);
FOR I IN 8 DOWNTO 1 LOOP
A(I)<=A(I-1);
END LOOP;
A(0)<='0';
ST<=S1;
WHEN S1=>
FOR J IN 11 DOWNTO 1 LOOP
C(J)<=C(J-1);
END LOOP;
C(0)<=K;
ST<=S2;
WHEN S2=>
IF C(3 DOWNTO 0)>4 THEN
C(3 DOWNTO 0)<=C(3 DOWNTO 0)+3;
END IF;
ST<=S3;
WHEN S3=>
IF C(7 DOWNTO 4)>4 THEN
C(7 DOWNTO 4)<=C(7 DOWNTO 4)+3;
END IF;
ST<=S4;
WHEN S4=>
IF C(11 DOWNTO 8)>4 THEN
C(11 DOWNTO 8)<=C(11 DOWNTO 8)+3;
END IF;
ST<=S5;
WHEN S5=>
IF T<8 THEN
T:=T+1;
ST<=S0;
ELSE
ST<=S6;
T:=0;
END IF;
WHEN S6=>
BCD_SEG(11 DOWNTO 1)<=C(10 DOWNTO 0);
BCD_SEG(0)<=A(8);
ST<=S6;
END CASE;
END IF;
END IF;
END PROCESS;
END GO;
