km.vhd

出租车计费系统的 实现

Library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
USE IEEE.STD_LOGIC_ARITH.ALL;
entity KM is
port (
         CLK,RESET,CON:in std_logic;
         COUT:OUT  STD_LOGIC
                );
end;
architecture behv of KM is
 SIGNAL CO1: STD_LOGIC;

   BEGIN
     PROCESS(CLK,CON,RESET)
      VARIABLE CNT:INTEGER RANGE 9 DOWNTO 0;
          BEGIN
     IF RESET ='1' THEN CNT:=0;CO1<='0';
       ELSIF CLK'EVENT AND CLK='1' THEN
          IF CON='1' 
         THEN 
           CNT:=CNT+1;
         IF CNT>9
           THEN CO1<='1';
         END IF;
      END IF;
   END IF;
COUT<=CO1;

END PROCESS;
END ;