cnt1.vhd.bak

(1)设计4位十进制频率计测量范围: 1Hz～9999Hz (2）测量的数值通过4个数码管显示 (3）频率超过9999Hz时

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
ENTITY CNT1 IS
  PORT(clk6:IN STD_LOGIC;
       Q6: OUT STD_LOGIC);
END CNT1;

ARCHITECTURE ddy OF CNT1 IS
SIGNAL s:STD_LOGIC;
SIGNAL mi:INTEGER RANGE 1 TO 13500000;
BEGIN
PROCESS(clk6)
BEGIN
    IF (clk6'EVENT AND clk6='1') THEN
        IF(MI=13500000) THEN
			MI<=1;
			S<=NOT S;
			ELSIF(MI<13500000) THEN
			    MI<=MI+1;
				ELSIF(MI=6750000) THEN
					S<=NOT S;		
		END IF;
	Q6<=S;
    END IF;
END PROCESS;
END ddy;