cpld

《CPLD开发实例》的配套光盘文件

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY MOORE1 IS
  PORT (DATAIN  :IN STD_LOGIC_VECTOR(1 DOWNTO 0);  
         CLK,RST : IN STD_LOGIC; 
                Q : OUT STD_LOGIC_VECTOR(3 DOWNTO 0));
END MOORE1;
ARCHITECTURE behav OF MOORE1 IS
  TYPE ST_TYPE IS (ST0, ST1, ST2, ST3,ST4);  
   SIGNAL C_ST : ST_TYPE ;
    BEGIN                     
    PROCESS(CLK,RST) 
     BEGIN      
    IF RST ='1' THEN  C_ST <= ST0 ; Q<= "0000" ;
      ELSIF CLK'EVENT AND CLK='1' THEN
      CASE C_ST IS           
         WHEN ST0 => IF DATAIN ="10" THEN C_ST <= ST1 ;
               ELSE C_ST <= ST0 ; END IF;
               Q <= "1001" ; 
         WHEN ST1 => IF DATAIN ="11" THEN C_ST <= ST2 ;
               ELSE C_ST <= ST1 ;END IF;
               Q <= "0101" ;
         WHEN ST2 => IF DATAIN ="01" THEN C_ST <= ST3 ;
               ELSE C_ST <= ST0 ;END IF;
               Q <= "1100" ;
         WHEN ST3 => IF DATAIN ="00" THEN C_ST <= ST4 ;
               ELSE C_ST <= ST2 ;END IF;
               Q <= "0010" ;
         WHEN ST4 => IF DATAIN ="11" THEN C_ST <= ST0 ;
               ELSE C_ST <= ST3 ;END IF;
                 Q <= "1001" ;
         WHEN OTHERS => C_ST <= ST0;
       END CASE;
    END IF;
  END PROCESS;
END behav;