3-8译码器

1、译码

将n位的编码转换为m位的编码，每一个有效的输入编码产生唯一一个输出编码，并且有n≤m≤2n。实现译码功能的电路称为译码器。

2、真值表

A2A1A0	D0D1D2D3D4D5D6D7
000	10000000
001	01000000
010	00100000
011	00010000
100	00001000
101	00000100
110	00000010
111	00000001

3、电路图

非层次化设计

层次化设计

4、代码

	library ieee;
	use ieee.std_logic_1164.all;

	entity threetoeight is
	port(A:in std_logic_vector(2 downto 0);
		 D:out std_Logic_vector(0 downto 7));
	end threetoeight;

	architecture heihei of threetoeight is
	signal D1:std_logic_vector(0 downto 7);
	begin
		D1<="10000000"when A="000" else
		"01000000"when A="001" else
		"00100000"when A="010" else
		"00010000"when A="011" else
		"00001000"when A="100" else
		"00000100"when A="101" else
		"00000010"when A="110" else
		"00000001"when A="111" else
		"00000000";
		D<=D1;
	end heihei;

来源：oschina

链接：https://my.oschina.net/u/4443770/blog/3164501