dfre.vhd

设计一个五路呼叫器,具体设计要求如下: 1．五个按键模拟五个呼叫源 2．当有一个按键按下时

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY DFRE IS
	PORT(iclk : IN STD_LOGIC;
		 iRES : IN STD_LOGIC;
		 oNUM: OUT STD_LOGIC_VECTOR(2 DOWNTO 0)
		);
END DFRE;

ARCHITECTURE run OF DFRE IS
	BEGIN
	PROCESS (iRES, iclk)
	VARIABLE fre: STD_LOGIC_VECTOR(25 DOWNTO 0);
	VARIABLE V_oNUM : STD_LOGIC_VECTOR(2 DOWNTO 0) := "000"; 
	BEGIN
	IF iclk'EVENT AND iclk = '1'
	THEN IF iRES = '0'
		 THEN fre := "00000000000000000000000000";
	     V_oNUM := "000";
		 ELSIF fre = "01011111010111100001000000"
		 THEN fre := "00000000000000000000000000";
			  IF V_oNUM = "101"
		      THEN V_oNUM := "001";
		      ELSE V_oNUM := V_oNUM + '1';
		      END IF;
		 ELSE fre := fre + '1';
		 END IF;
	END IF;
	oNUM <= V_oNUM;
	END PROCESS;
END run;