--BCD Counter
LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_arith.all;
USE ieee.std_logic_unsigned.all;

ENTITY freq IS
 PORT( Fsignal        :    IN    std_logic;
--        Rst            :    IN    std_logic;
       Gate        :    IN    std_logic;
       Ready        :    OUT std_logic;
       Data_out    :    OUT std_logic_vector(31 downto 0);
       overflow    :    OUT std_logic
      );
END freq;

ARCHITECTURE freq_counter OF freq IS
CONSTANT    HIGH            :    std_logic    := '1';
CONSTANT    LOW                :    std_logic    := '0';

--SIGNAL        Rst                :    std_logic;

SIGNAL        one                :    std_logic_vector (3 downto 0);
SIGNAL        ten                :    std_logic_vector (3 downto 0);
SIGNAL        hun                :    std_logic_vector (3 downto 0);
SIGNAL        thou            :    std_logic_vector (3 downto 0);
SIGNAL        mill            :    std_logic_vector (3 downto 0);
SIGNAL        ten_mill        :    std_logic_vector (3 downto 0);
SIGNAL        hun_mill        :    std_logic_vector (3 downto 0);
SIGNAL        thou_mill        :    std_logic_vector (3 downto 0);

SIGNAL        state            :    std_logic_vector (1 downto 0);
SIGNAL        enable_cnt        :    std_logic;
--SIGNAL        Temp_data        :    std_logic_vector(31 downto 0);


BEGIN
   
--    Data_out    <=    thou_mill &    hun_mill & ten_mill    & mill & thou & hun & ten & one;
--    Temp_data    :=    thou_mill &    hun_mill & ten_mill    & mill & thou & hun & ten & one;
--    Data_out    <=    Temp_data;
   Ready        <=    NOT    enable_cnt;
PROCESS (Gate)
BEGIN
 IF (Gate = LOW and Gate'EVENT)    then
   Data_out    <=    thou_mill &    hun_mill & ten_mill    & mill & thou & hun & ten & one;
 END IF;
END PROCESS;
--    Rst            :=    Gate;
--    enable_cnt    :=    Gate;

-- *******************************************************************************************
-- FREQUENCY COUNTER    
-- Counts from 00000000 to 99999999 (BCD) only when the GATE is high
-- *******************************************************************************************
PROCESS    (Fsignal, Gate)
BEGIN
 IF (Gate = LOW)    THEN
   state <= "00";
 ELSIF (Fsignal= HIGH and Fsignal'EVENT)    THEN
   state <= "11";
END IF;
END PROCESS;

STAT:    PROCESS (state)
BEGIN    
 IF (state = "11")    THEN
   --IF (Gate=HIGH)
   --    THEN    
   enable_cnt <= HIGH;
   --END IF;
   ELSIF (state = "00")    --THEN
   --ELSIF (Gate=LOW)
   THEN    enable_cnt <= LOW;
   --END IF;
 END IF;
END PROCESS STAT;

-- OVERFLOW DETECT
OVERFLOW_DET:    PROCESS (Gate, Fsignal)
 BEGIN
   IF (Gate=LOW)    THEN
       overflow <= LOW;
   ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
     IF (thou_mill="1001" and hun_mill="1001" and ten_mill="1001" and mill="1001" 
               and thou="1001" and hun="1001" and ten="1001" and one="1001")
       THEN    overflow <= HIGH;
     END IF;
   END IF;
END PROCESS OVERFLOW_DET;

--**********************************
-- COUNTERS

-- ONES BCD COUNTERS
ONE_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   one    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (one="1001")    THEN 
           one <= "0000";
       ELSE    one <= one + 1;
       END IF;
   END IF;
 END IF;
END PROCESS ONE_CNTER;

-- TENS BCD COUNTERS
TEN_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   ten    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (ten="1001" and one="1001")    THEN 
           ten <= "0000";
       ELSIF (one="1001")    THEN
           ten <= ten + 1;
       END IF;
   END IF;
 END IF;
END PROCESS TEN_CNTER;

-- HUNDREDS BCD COUNTERS
HUND_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   hun    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (hun="1001" and ten="1001" and one="1001")    THEN 
           hun <= "0000";
       ELSIF (ten="1001" and one="1001")    THEN
           hun <= hun + 1;
       END IF;
   END IF;
 END IF;
END PROCESS HUND_CNTER;

-- THOUSANDS BCD COUNTERS
THOU_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   thou    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN 
           thou <= "0000";
       ELSIF (hun="1001" and ten="1001" and one="1001")    THEN
           thou <= thou + 1;
       END IF;
   END IF;
 END IF;
END PROCESS THOU_CNTER;

-- MILLIONS BCD COUNTERS
MILL_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   mill    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN 
           mill <= "0000";
       ELSIF (thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN
           mill <= mill + 1;
       END IF;
   END IF;
 END IF;
END PROCESS MILL_CNTER;

-- TEN_MILLIONS BCD COUNTERS
TEN_MILL_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   ten_mill    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (ten_mill="1001" and mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN 
           ten_mill <= "0000";
       ELSIF (mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN
           ten_mill <= ten_mill + 1;
       END IF;
   END IF;
 END IF;
END PROCESS TEN_MILL_CNTER;

-- HUND_MILLIONS BCD COUNTERS
HUN_MILL_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   hun_mill    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (hun_mill="1001" and ten_mill="1001" and mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN 
           hun_mill <= "0000";
       ELSIF (ten_mill="1001" and mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN
           hun_mill <= hun_mill + 1;
       END IF;
   END IF;
 END IF;
END PROCESS HUN_MILL_CNTER;

-- THOU_MILLIONS BCD COUNTERS
THOU_MILL_CNTER:    PROCESS (Fsignal, Gate)
BEGIN
 IF (Gate=LOW )    THEN
   thou_mill    <= "0000";
 ELSIF (Fsignal=HIGH and Fsignal'EVENT)    THEN
   IF (enable_cnt=HIGH)    THEN
       IF (thou="1001" and hun_mill="1001" and ten_mill="1001" and mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN 
           thou_mill <= "0000";
       ELSIF (hun_mill="1001" and ten_mill="1001" and mill="1001" and thou="1001" and hun="1001" and ten="1001" and one="1001")    THEN
           thou_mill <= thou_mill + 1;
       END IF;
   END IF;
 END IF;
END PROCESS THOU_MILL_CNTER;

END freq_counter;