key_out.vhd

简单易懂的4*4键盘扫描及显示程序。对编写其他形式的键盘扫描程序有一定的指导意义.

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use IEEE.STD_LOGIC_ARITH.ALL;
entity key_out is
	port(
		clk:in std_logic;
--		scan_in:in std_logic_vector(3 downto 0);
		scan_out:in std_logic_vector(3 downto 0);
		q:out std_logic_vector(3 downto 0)
		);
end entity;
architecture rt1 of key_out is
signal temp:std_logic_vector(3 downto 0);
signal scan_in: std_logic_vector(3 downto 0);
begin
	process (clk,scan_in)
	begin
		if rising_edge(clk) then
			if (scan_in<="0001") then
				if(scan_out<="0001") then
					temp<="0000";
				elsif (scan_out<="0010")then
					temp<="0100";
				elsif (scan_out<="0100")then
					temp<="1000";
				elsif (scan_out<="1000")then
					temp<="1100";
--				else temp<="zzzz";
				end if;
				
			elsif (scan_in<="0010") then
				if(scan_out<="0001") then
					temp<="0001";
				elsif (scan_out<="0010")then
					temp<="0101";
				elsif (scan_out<="0100")then
					temp<="1001";
				elsif (scan_out<="1000")then
					temp<="1101";
--				else temp<="zzzz";
				end if;

			elsif (scan_in<="0100") then
				if(scan_out<="0001") then
					temp<="0010";
				elsif (scan_out<="0010")then
					temp<="0110";
				elsif (scan_out<="0100")then
					temp<="1010";
				elsif (scan_out<="1000")then
					temp<="1110";
--				else temp<="zzzz";
				end if;
			
			elsif (scan_in<="1000") then
				if(scan_out<="0001") then
					temp<="0011";
				elsif (scan_out<="0010")then
					temp<="0111";
				elsif (scan_out<="0100")then
					temp<="1011";
				elsif (scan_out<="1000")then
					temp<="1111";
--				else temp<="zzzz";
				end if;
			end if;
		end if;
end process;
q<=temp;
end rt1;