第一次用该软件 不会写 求照顾
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY CNT99 IS
PORT (CLK,RST: IN STD_LOGIC;
PLD,ENB: IN STD_LOGIC;
CQ: OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
DQ: OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
FENMIN : OUT STD_LOGIC);
END;
ARCHITECTURE ARCH OF CNT99 IS
BEGIN
PROCESS(CLK, RST,ENB)
VARIABLE CQI: STD_LOGIC_VECTOR(3 DOWNTO 0);
VARIABLE CQO: STD_LOGIC_VECTOR(3 DOWNTO 0);
BEGIN
IF RST= '1' THEN CQI:="1001" ; CQO:="1001";
ELSIF CLK'EVENT AND CLK='1' THEN
IF PLD= '1' THEN CQI:="1001" ; CQO:="1001";
ELSIF ENB='1' THEN
IF CQI= "0000" AND CQO/="0000"
THEN CQI:="1001";
CQO:=CQO-1;
ELSE CQI:=CQI-1; ----CQI??? CQO???
END IF;
END IF;
IF CQI= "0000" AND CQO= "0000"
THEN FENMIN <= '1';
ELSE FENMIN <= '0';
CQ <= CQI;
DQ<= CQO;
END IF;
END IF;
END PROCESS;
END ARCH;