mux8_1.vhd

8.22出租车计价器VHDL程序与仿真。 --文件名：taxi.hd。 --功能：出租车计价器。 --最后修改日期：2004.4.9。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
ENTITY mux8_1 IS;
port(c:in std_logic_vector(2 downto0);
     dp: out std_logic;
     a1,a2,a3,a4,b1,b2,t1,t2:in std_logic_vertor(3 downto ));
     d:out std_logic_vector(3 downto 0));
end mux8_1;
architecture rt1 of mux8_1 is
begin 
process(c,a1,a2,a3,a4,b1,b2,t1,t2)
variadle comb:std_logic_vector(2 downto 0);
begin 
comb:=c;
case comb is
     when"000"=>d<=a1;dp<='0';
      when"001"=>d<=a2;dp<='0';
      when"010"=>d<=a3;dp<='1';
     when"011"=>d<=a4;dp<='0';
     when"100"=>d<=b1;dp<='0';
     when"101"=>d<=b2;dp<='0';
     when"110"=>d<=t1;dp<='0';
      when"111"=>d<=t2;dp<='0';
       when others=>null;
end case;
end process;
end rt1;