chufa.vhd

微机接口实验程序 。。 。。 。。 。。 。。 。。 。。

--chu fa kongzhi 


library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;



entity chufa is
 port(
        clk:    in std_logic;   --CHU FA SOURCE CHOOSE     
        WAY1:   in std_logic;   
        WAY2:   in std_logic;
        WAY3:   in std_logic;
        CHUFA: OUT STD_LOGIC --CHU FA ENABLE
      );
END CHUFA;       


architecture CHUFA of CHUFA is
                          
       signal A:STD_LOGIC_VECTOR (0 TO 2);

            begin
              process(clk)              
                BEGIN
                   if CLK'event and CLK ='0'   THEN
                       if A=2 THEN
                          A<="000"; 
                       ELSif A=0 THEN
                           A<=A+1;                 
                       ELSIF A=1 THEN
                        A<=A+1;                 
                       end IF;
                   END IF;
                  End process;
                      
              PROCESS (A)
                 BEGIN
                 IF A=2 THEN
                   CHUFA<=WAY3;
                 ELSIF A=1 THEN
                   CHUFA<=WAY2;
                  ELSIF A=0 THEN
                    CHUFA<=WAY1;
                  END IF;
               END PROCESS;
END CHUFA;