upcount.vhd

来自「一本很好的关于学习VHDL的书,Fundamentals of Digital 」· VHDL 代码 · 共 27 行

LIBRARY ieee ;
USE ieee.std_logic_1164.all ;
USE ieee.std_logic_unsigned.all ;

ENTITY upcount IS
	PORT ( 	Clock, Resetn, E 	: IN 	STD_LOGIC ;
			Q 					: OUT 	STD_LOGIC_VECTOR (3 DOWNTO 0)) ;
END upcount ;

ARCHITECTURE Behavior OF upcount IS
	SIGNAL Count : STD_LOGIC_VECTOR (3 DOWNTO 0) ;
BEGIN
	PROCESS ( Clock, Resetn )
	BEGIN
		IF Resetn = '0' THEN
			Count <= "0000" ;
		ELSIF (Clock'EVENT AND Clock = '1') THEN
			IF E = '1' THEN
				Count <= Count + 1 ;
			ELSE
				Count <= Count ;
			END IF ;
		END IF ;
	END PROCESS ;
	Q <= Count ;
END Behavior ;