library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;

entity V74xs3 is
    port (
        CLK, CLR_L, LD_L, ENP, ENT: in STD_LOGIC;
        D: in UNSIGNED (3 downto 0);
        Q: out UNSIGNED (3 downto 0);
        RCO: out STD_LOGIC
    );
end V74xs3;

architecture V74xs3_arch of V74xs3 is
signal IQ: UNSIGNED (3 downto 0);
begin
process (CLK, ENT, IQ)
  begin
    if CLK'event and CLK='1' then
      if CLR_L='0' then IQ <= (others => '0');
      elsif LD_L='0' then IQ <= D;
      elsif (ENT and ENP)='1' and (IQ=12) then IQ <= ('0','0','1','1');
      elsif (ENT and ENP)='1' then IQ <= IQ + 1;
      end if;
    end if;
    if (IQ=12) and (ENT='1') then RCO <= '1';
    else RCO <= '0';
    end if;
    Q <= IQ;     
  end process;
end V74xs3_arch;