counter12.vhd

来自「用于视频运动图像编码的HUFFMAN编码」· VHDL 代码 · 共 43 行

---------      电子系                 学号：J02301                姓名：张宗旺----
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity COUNTER12 is
	port	(RST,UPDOWN: in std_logic;
		CLK: in std_logic;
		COUNTER_Q: out std_logic_vector(3 downto 0));
end COUNTER12;

architecture ALG of COUNTER12 is
	signal CNT: std_logic_vector(3 downto 0);
begin
	COUNT:process(RST,CLK)
	begin 
		if RST='0' then
			CNT<="0000";
		else
			if CLK'event and CLK='1' then
				if UPDOWN='1' then
					if CNT="1011" then 
						CNT<="0000";
					else 					
						CNT<=CNT+1;
					end if;
				else
					if CNT="0000" then
						CNT<="1011";
					else 
						CNT<=CNT-1;
					end if;
				end if;
			end if;
		end if;
	end process;
	
	COUNTER_Q<=CNT;
end ALG;