大侠帮忙看下这段VHDL代码

只看该作者 · 2010-12-18 19:57

本帖最后由 le062 于 2010-12-27 17:03 编辑

我要做个智力抢答器，下面是抢答判断的代码
我用了个VARIABLE SC:INTEGER 用来锁存判断
但是仿真的时候当 CLR=0 AND RST=0,输出A1, B1, C1, D1就都是不定值了

复制

LIBRARY IEEE; 

USE IEEE.STD_LOGIC_1164.ALL; 

ENTITY QDJB IS

PORT (CLR,RST: IN STD_LOGIC;

A, B, C, D: IN STD_LOGIC; 

A1, B1, C1, D1: OUT STD_LOGIC; 

G: OUT STD_LOGIC_VECTOR (3 DOWNTO 0)); 

END QDJB; 

ARCHITECTURE ART OF QDJB IS

CONSTANT W1: STD_LOGIC_VECTOR:="1010"; 

CONSTANT W2: STD_LOGIC_VECTOR:="1011"; 

CONSTANT W3: STD_LOGIC_VECTOR:="1100"; 

CONSTANT W4: STD_LOGIC_VECTOR:="1101"; 

CONSTANT FOUL: STD_LOGIC_VECTOR:="1111";

BEGIN

PROCESS(CLR,RST)

VARIABLE SC:INTEGER:=00;

BEGIN

IF(CLR='1'OR RST='1')THEN

IF(A='0'AND B='0'AND C='0'AND D='0')THEN

A1<='0'; B1<='0'; C1<='0'; D1<='0';G<="1110";SC:=01;

ELSIF((A='1'AND (SC=01))OR (SC=02))THEN

A1<='1'; B1<='0'; C1<='0'; D1<='0';G<=FOUL;SC:=02;

ELSIF((B='1'AND (SC=01))OR (SC=03))THEN

A1<='0'; B1<='1'; C1<='0'; D1<='0';G<=FOUL;SC:=03;

ELSIF((C='1'AND (SC=01))OR (SC=04))THEN

A1<='0'; B1<='0'; C1<='1'; D1<='0';G<=FOUL;SC:=04;

ELSIF((D='1'AND (SC=01))OR (SC=05))THEN

A1<='0'; B1<='0'; C1<='0'; D1<='1';G<=FOUL;SC:=05; 

END IF; 

ELSE

IF ((A='1'AND (SC=01))OR (SC=06))THEN

A1<='1'; B1<='0'; C1<='0'; D1<='0';G<=W1;SC:=06; 

ELSIF((B='1'AND (SC=01))OR (SC=07))THEN

A1<='0'; B1<='1'; C1<='0'; D1<='0';G<=W2;SC:=07; 

ELSIF((C='1'AND (SC=01))OR (SC=08))THEN

A1<='0'; B1<='0'; C1<='1'; D1<='0';G<=W3;SC:=08; 

ELSIF((D='1'AND (SC=01))OR (SC=09))THEN

A1<='0'; B1<='0'; C1<='0'; D1<='1';G<=W4;SC:=09; 

ELSE A1<='0'; B1<='0'; C1<='0'; D1<='0';G<="0000";

END IF;

END IF;

END PROCESS; 

END ART;