Internal Error in Quartus...HELP

choose: process(EAB01,dados,start)
begin
if (Start = '0') then
    if (EAB01 = "01") then
        buffer_ton_16 <= data;
    else if (EAB01 = "10") then
        buffer_toff_16 <= data;
    else if (EAB01 = "11") then
        if (ton_toff = '0') then
            buffer_ton_32 <= data;
        else if (ton_toff = '1') then
            buffer_toff_32 <= data;
        end if;
        end if;
        ton_toff <= not ton_toff;
    else if (EAB01 = "00") then
        TON  <= CONV_INTEGER(buffer_ton_16 & buffer_ton_32);
        TOFF <= CONV_INTEGER(buffer_toff_16 & buffer_toff_32);
    end if;
    end if;
    end if;
    end if;
    end if;
end process;

library ieee; 
use ieee.std_logic_1164.all; 
  
entity clk_div is 
port 
(clk_crystal, reset: in std_logic; 
 clk_desired: buffer std_logic); 
end clk_div; 
  
architecture arc_clk_div of clk_div is 
begin

-- P = f(crystal)/(2*f(desired))
-- this is the formula for counting the constant P
-- f(crystal) is the external crystal frequency
-- f(desired) is the slower clk frequency required by the designer

	process(reset, clk_crystal) 
		variable count: natural;
		constant P : natural := 33330;
	begin 
		if reset = '1' then 
			count := 0; 
			clk_desired <= '0'; 
		elsif rising_edge(clk_crystal) then 
			count := count + 1; 
			if count = P then 
				clk_desired <= not clk_desired; 
				count := 0; 
			end if; 
		end if; 
	end process; 
end arc_clk_div;