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[/] [special_functions_unit/] [Open_source_SFU/] [log2_vhdl/] [parts/] [log2_ieee.vhd] - Rev 4

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-- Log2 IEEE754 case detect
library ieee;
	use ieee.std_logic_1164.all;
	use ieee.numeric_std.all;
 
entity log2_ieee is
	port 	  (i_data					: in	std_logic_vector(31 downto 0);
				o_case					: out std_logic_vector(31 downto 0);
				o_case_en				: out std_logic);
end entity;
 
architecture rtl of log2_ieee is
 
	signal s_sgn	: std_logic;
	signal s_exp	: std_logic_vector(7 downto 0);
	signal s_mantis: std_logic_vector(22 downto 0);
 
begin
	s_sgn <= i_data(i_data'left);
	s_exp <= i_data(i_data'left-1 downto 23);
	s_mantis	<= i_data(22 downto 0);
 
	process(s_sgn, s_exp, s_mantis)
	begin	
 
		if s_exp = X"00" then
			o_case		<= X"FF800000";
			o_case_en	<= '1';
 
		elsif s_exp = X"FF" then
			o_case_en	<= '1';
			if s_sgn = '0' and s_mantis = "00000000000000000000000" then
				o_case <= X"7F800000";
			else	
				o_case <= X"FFFFFFFF";
			end if;
 
		elsif	s_exp = X"7F" and s_mantis = "00000000000000000000000" and s_sgn = '0' then
			o_case_en	<= '1';
			o_case <= X"00000000";
 
		elsif s_sgn = '1' then
			o_case_en	<= '1';
			o_case <= X"FFFFFFFF";
 
		else
			o_case_en	<= '0';
			o_case <= X"00000000";
		end if;
 
	end process;
end rtl;
 
 

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