Exponent encoder circuit and mask circuit

A mask circuit having n-bit input data where the most significant bit of bit positions at one level is a marker logic level bit, with all bits at bit positions of lower significance than the marker logic level bit being put at one logic level and all bits at bit positions of greater significance than the bit position of the marker logic level bit being put at another logic level, said circuit comprising:

• output data lines of the same number as there are items of input data;
• output line initialization transistors for charging (or discharging) each output line and putting each output line to a logic level based on an output line pre-processing signal;
• n output fixing transistors provided for n (where n=1 to N) output lines, for discharging (or charging) the respective output lines by inputting marker logic level bits to respective gates;
• and
• input lines for inputting n bit values from the most significant bit side of the input data to respective gates of the n output fixing transistors for the nth (where n=1 to N) output line,
• wherein the input data is inputted to each input line after all of the output lines are put to one logic level based on the pre-processing signal for the output lines so that output data is formed at each of the output lines.

An exponent encoder circuit for obtaining an exponent constituted by a left shift amount for normalizing input data with code configured with a two bit exponent, said circuit comprising:

• a code matching circuit for converting to data for a positive number so that exponents become the same when inputted data is a negative number (or a positive number) and allowing data to pass as is when the inputted data is a positive number (or negative number);
• a mask circuit where a most significant bit position is included giving a marker logic level bit within the output of the code matching circuit with all bits at bit positions of lower significance being put at one logic level and all bits at bit positions of greater significance than the bit position of the most significant bit position given by the marker logic level bit being put at another logic level;
• and
• an encoder circuit for generating an exponent from the output of the mask circuit.