upcount.vhd

来自「一本很好的关于学习VHDL的书,Fundamentals of Digital 」· VHDL 代码 · 共 23 行

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

ENTITY upcount IS
	PORT (	Clear, Clock	: IN 		STD_LOGIC ;
			Q 				: BUFFER 	STD_LOGIC_VECTOR(1 DOWNTO 0) ) ;
END upcount ;

ARCHITECTURE Behavior OF upcount IS
BEGIN
	upcount: PROCESS ( Clock )
	BEGIN
		IF (Clock'EVENT AND Clock = '1') THEN
			IF Clear = '1' THEN
				Q <= "00" ;
			ELSE
				Q <= Q + '1' ;
			END IF ;
		END IF;
	END PROCESS;
END Behavior ;