decod_component.vhd

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;

entity decod_component is
    port(
        clk        : in  std_logic; -- Clock signal
        A, B, C, D : in  std_logic_vector(3 downto 0); -- Input digits (4-bit each)
        sel_display: out std_logic_vector(3 downto 0); -- Output to select the display
        segment    : out std_logic_vector(7 downto 0)  -- Output to drive the 7-segment display
    );
end decod_component;

architecture hardware of decod_component is

type digit_array is array (0 to 3) of std_logic_vector(3 downto 0); -- Array type to hold 4 digits
signal digits  : digit_array; -- Signal to hold the input digits

type segmenton_array is array (0 to 15) of std_logic_vector(7 downto 0); -- Array type to hold the 7-segment encoding for 0-F
constant segmenton : segmenton_array := (
    "00000011", -- 0
    "10011111", -- 1
    "00100101", -- 2
    "00001101", -- 3
    "10011001", -- 4
    "01001001", -- 5
    "01000001", -- 6
    "00011111", -- 7
    "00000001", -- 8
    "00001001", -- 9
    "00010001", -- A
    "11000001", -- B
    "01100011", -- C
    "10000101", -- D
    "01100001", -- E
    "01110001"  -- F
); -- Constant array with 7-segment encoding

signal psc     : integer range 0 to 50001 := 0; -- Prescaler for clock division
signal sel_dig : integer range 0 to 3 := 0; -- Signal to select the current digit

begin
    -- Assign input digits to the array
    digits(0) <= A;
    digits(1) <= B;
    digits(2) <= C;
    digits(3) <= D;

    -- Clock process to update the prescaler and digit selector
    process(clk)
    begin
        if rising_edge(clk) then
            psc <= psc + 1;
            if psc = 50000 then
		psc <= 0;
                sel_dig <= sel_dig + 1; -- Increment digit selector
            end if;
        end if;
    end process;

    -- Process to update the selected display and segment values
    process(sel_dig, digits)
    begin
        case sel_dig is
            when 0 => sel_display <= "0111"; -- Enable first display
            when 1 => sel_display <= "1011"; -- Enable second display
            when 2 => sel_display <= "1101"; -- Enable third display
            when 3 => sel_display <= "1110"; -- Enable fourth display
            when others => sel_display <= "1111"; -- Default case (disable all)
        end case;

        -- Set the segment output based on the current digit
        segment <= segmenton(to_integer(unsigned(digits(sel_dig))));
    end process;
end hardware;