Thanks for your suggestions. I am not asking anyone to write code for me. See my subject again and just signal detection can’t be someone’s entire project.
BTW, I had posted this same question on another forum and got a suggestion to ‘implement detector of the rising edge for the sync signal. You could implement counter (startingelectronics dot org/software/VHDL-CPLD-course/tut19-up-down-counter/ ) which would increment every rising edge of SYNC and on every time pulse (say 1ms using m clock), you would check if the counter changed.’
I have implement the logic, below is the code. But it is working only first time connection of sensor. When I disconnect the SYNC signal the output doesn’t goes to low. Please advice the changes, I am beginner in VHDL and not an expert.
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity sync_detector is
Port ( SYNC : in STD_LOGIC; -- Input SYNC signal
PULSE : in STD_LOGIC; -- Input 1.024ms pulse
OUTPUT : out bit -- tells SYNC status
);
end sync_detector;
architecture Behavioral of sync_detector is
signal S0_s : std_logic := '1';
signal counter_running : std_logic := '0';
signal count : STD_LOGIC_VECTOR (3 downto 0):= X"0";
begin
S0_s <= not(SYNC);
-- Process for 4-bit counter
process(S0_s)
begin
if (S0_s'event and S0_s= '1') then
count <= count + '1';
counter_running <= '1';
end if;
end process;
-- Process to check counter running after each 1.024ms
process(PULSE)
begin
if (PULSE'event and PULSE = '1') then
if counter_running = '1' then
OUTPUT <= '1';
else
OUTPUT <= '0';
end if;
end if;
end process;
end Behavioral;
