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[/] [tanhapprox/] [trunk/] [logsig_approx.vhd] - Rev 2
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-- Copied from Altera VHDL Custom Instruction Template File for Combinatorial Logic library ieee; use ieee.std_logic_1164.all; use ieee.std_logic_unsigned.all; entity logsig_approx is port( signal dataa: in std_logic_vector(31 downto 0); -- Operand A (input to tansig) signal result: out std_logic_vector(31 downto 0) -- result (tansig approximation) ); end entity logsig_approx; architecture behavior of logsig_approx is -- the "exponent" part of the input (in IEEE754 format) signal in_exponent : std_logic_vector(7 downto 0); -- the most significant bits of the mantissa (for this LUT, we only need the first 5 bits signal in_mantissa_msbits : std_logic_vector(4 downto 0); begin -- separate the exponent and mantissa portions of the input in_exponent <= dataa(30 downto 23); in_mantissa_msbits <= dataa(22 downto 18); -- propagate the sign directly to the output since the tansig is an odd function result(31) <= dataa(31); -- use a linear approximation if exponent is smaller than 2^-2 process(dataa) begin if( in_exponent >= "10000001" ) THEN result(30 downto 0) <= "0111111100000000000000000000000"; -- for high values go to 1 elsif (in_exponent = "10000001") AND (in_mantissa_msbits >= "00000") THEN result(30 downto 0) <= "0111111011111111101011010110101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11111") THEN result(30 downto 0) <= "0111111011111111101000100110110"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11110") THEN result(30 downto 0) <= "0111111011111111100101011111100"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11101") THEN result(30 downto 0) <= "0111111011111111100001111101110"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11100") THEN result(30 downto 0) <= "0111111011111111011101111101111"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11011") THEN result(30 downto 0) <= "0111111011111111011001011100000"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11010") THEN result(30 downto 0) <= "0111111011111111010100010011101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11001") THEN result(30 downto 0) <= "0111111011111111001110011111101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "11000") THEN result(30 downto 0) <= "0111111011111111000111111010001"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10111") THEN result(30 downto 0) <= "0111111011111111000000011100101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10110") THEN result(30 downto 0) <= "0111111011111110110111111111101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10101") THEN result(30 downto 0) <= "0111111011111110101110011010110"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10100") THEN result(30 downto 0) <= "0111111011111110100011100100100"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10011") THEN result(30 downto 0) <= "0111111011111110010111010010001"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10010") THEN result(30 downto 0) <= "0111111011111110001001010111011"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10001") THEN result(30 downto 0) <= "0111111011111101111001100110100"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "10000") THEN result(30 downto 0) <= "0111111011111101100111110000000"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01111") THEN result(30 downto 0) <= "0111111011111101010011100010000"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01110") THEN result(30 downto 0) <= "0111111011111100111100101000101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01101") THEN result(30 downto 0) <= "0111111011111100100010101101100"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01100") THEN result(30 downto 0) <= "0111111011111100000101010111000"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01011") THEN result(30 downto 0) <= "0111111011111011100100001000011"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01010") THEN result(30 downto 0) <= "0111111011111010111110100001010"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01001") THEN result(30 downto 0) <= "0111111011111010010011111101000"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "01000") THEN result(30 downto 0) <= "0111111011111001100011110010010"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00111") THEN result(30 downto 0) <= "0111111011111000101101010010101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00110") THEN result(30 downto 0) <= "0111111011110111101111101001100"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00101") THEN result(30 downto 0) <= "0111111011110110101001111100010"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00100") THEN result(30 downto 0) <= "0111111011110101011011001000101"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00011") THEN result(30 downto 0) <= "0111111011110100000010000100001"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00010") THEN result(30 downto 0) <= "0111111011110010011101011011100"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00001") THEN result(30 downto 0) <= "0111111011110000101011110001011"; elsif (in_exponent = "10000000") AND (in_mantissa_msbits >= "00000") THEN result(30 downto 0) <= "0111111011101110101011011101110"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "11110") THEN result(30 downto 0) <= "0111111011101100011010101100000"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "11100") THEN result(30 downto 0) <= "0111111011101001110111011010110"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "11010") THEN result(30 downto 0) <= "0111111011100110111111011010001"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "11000") THEN result(30 downto 0) <= "0111111011100011110000001011000"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "10110") THEN result(30 downto 0) <= "0111111011100000000110111101010"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "10100") THEN result(30 downto 0) <= "0111111011011100000000101111111"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "10010") THEN result(30 downto 0) <= "0111111011010111011010001110101"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "10000") THEN result(30 downto 0) <= "0111111011010010001111110010111"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "01110") THEN result(30 downto 0) <= "0111111011001100011101100010000"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "01100") THEN result(30 downto 0) <= "0111111011000101111111001110100"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "01010") THEN result(30 downto 0) <= "0111111010111110110000011000000"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "01000") THEN result(30 downto 0) <= "0111111010110110101100001100110"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "00110") THEN result(30 downto 0) <= "0111111010101101101101101100011"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "00100") THEN result(30 downto 0) <= "0111111010100011101111101010101"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "00010") THEN result(30 downto 0) <= "0111111010011000101100110100011"; elsif (in_exponent = "01111111") AND (in_mantissa_msbits >= "00000") THEN result(30 downto 0) <= "0111111010001100011111110101110"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11111") THEN result(30 downto 0) <= "0111111010000100001111110000110"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11110") THEN result(30 downto 0) <= "0111111010000000110011100100111"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11101") THEN result(30 downto 0) <= "0111111001111101010010001010001"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11100") THEN result(30 downto 0) <= "0111111001111001101011011011101"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11011") THEN result(30 downto 0) <= "0111111001110101111111010100111"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11010") THEN result(30 downto 0) <= "0111111001110010001101110001001"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11001") THEN result(30 downto 0) <= "0111111001101110010110101100010"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "11000") THEN result(30 downto 0) <= "0111111001101010011010000001101"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10111") THEN result(30 downto 0) <= "0111111001100110010111101101100"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10110") THEN result(30 downto 0) <= "0111111001100010001111101011110"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10101") THEN result(30 downto 0) <= "0111111001011110000001111000101"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10100") THEN result(30 downto 0) <= "0111111001011001101110010000110"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10011") THEN result(30 downto 0) <= "0111111001010101010100110000101"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10010") THEN result(30 downto 0) <= "0111111001010000110101010101011"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10001") THEN result(30 downto 0) <= "0111111001001100001111111100000"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "10000") THEN result(30 downto 0) <= "0111111001000111100100100001111"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01111") THEN result(30 downto 0) <= "0111111001000010110011000100111"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01110") THEN result(30 downto 0) <= "0111111000111101111011100010111"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01101") THEN result(30 downto 0) <= "0111111000111000111101111010011"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01100") THEN result(30 downto 0) <= "0111111000110011111010001001101"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01011") THEN result(30 downto 0) <= "0111111000101110110000010000000"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01010") THEN result(30 downto 0) <= "0111111000101001100000001100100"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01001") THEN result(30 downto 0) <= "0111111000100100001001111110111"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "01000") THEN result(30 downto 0) <= "0111111000011110101101100111011"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00111") THEN result(30 downto 0) <= "0111111000011001001011000110001"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00110") THEN result(30 downto 0) <= "0111111000010011100010011100011"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00101") THEN result(30 downto 0) <= "0111111000001101110011101011000"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00100") THEN result(30 downto 0) <= "0111111000000111111110110100000"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00011") THEN result(30 downto 0) <= "0111111000000010000011111001011"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00010") THEN result(30 downto 0) <= "0111110111111000000101111011100"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00001") THEN result(30 downto 0) <= "0111110111101011111000001000101"; elsif (in_exponent = "01111110") AND (in_mantissa_msbits >= "00000") THEN result(30 downto 0) <= "0111110111011111011110100000111"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "11110") THEN result(30 downto 0) <= "0111110111010010111001001100101"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "11100") THEN result(30 downto 0) <= "0111110111000110001000010100111"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "11010") THEN result(30 downto 0) <= "0111110110111001001100000011100"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "11000") THEN result(30 downto 0) <= "0111110110101100000100100011101"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "10110") THEN result(30 downto 0) <= "0111110110011110110010000001010"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "10100") THEN result(30 downto 0) <= "0111110110010001010100101001101"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "10010") THEN result(30 downto 0) <= "0111110110000011101100101010101"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "10000") THEN result(30 downto 0) <= "0111110101110101111010010011100"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "01110") THEN result(30 downto 0) <= "0111110101100111111101110100011"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "01100") THEN result(30 downto 0) <= "0111110101011001110111011110010"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "01010") THEN result(30 downto 0) <= "0111110101001011100111100011100"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "01000") THEN result(30 downto 0) <= "0111110100111101001110010111001"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "00110") THEN result(30 downto 0) <= "0111110100101110101100001101011"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "00100") THEN result(30 downto 0) <= "0111110100100000000001011011000"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "00010") THEN result(30 downto 0) <= "0111110100010001001110010110011"; elsif (in_exponent = "01111101") AND (in_mantissa_msbits >= "00000") THEN result(30 downto 0) <= "0111110100000010010011010110010"; elsif (in_exponent = "01111100") AND (in_mantissa_msbits >= "11100") THEN result(30 downto 0) <= "0111110011100110100001100101000"; else -- for smaller values, use linear approximation result(30 downto 0) <= dataa(30 downto 0); end if; end process; end architecture behavior;