Fast static cross-unit comparator
First Claim
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1. A static comparator circuit capable of operating at high speeds while consuming very little power, said comparator circuit comprising:
- a first stage accepting a first bit string and a second bit string, said first stage generating a first output, said first output comprising a plurality of voltages corresponding to an XOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string, said first stage also generating a second output, said second output comprising a plurality of voltages corresponding to an XNOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string; and
a second stage comprising a hit-miss detection circuit, said hit-miss detection circuit comprising a hit line and a miss line, said hit-miss detection circuit further comprising NMOS transistors having NMOS transistor gates and PMOS transistors having PMOS transistor gates, each of said NMOS transistor gates and each of said PMOS transistor gates being controlled by each of said first plurality of voltages and each of said second plurality of voltages respectively, said NMOS transistors being connected in parallel to each other and said PMOS transistors being connected in parallel to each other such that when any one of said NMOS transistor gates goes high and any one of said PMOS transistor gates goes low, said hit line is pulled down and said miss line is pulled up.
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Abstract
A high speed, static, BiCMOS comparator circuit. Though static, the circuit operates at nearly dynamic speeds. The circuit consists of two stages. The first stage generates XOR and XNOR outputs given two bit strings. The second stage detects hit and miss separately using the XOR and XNOR inputs. The second stage generates signals for both hit lines and miss lines.
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Citations
23 Claims
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1. A static comparator circuit capable of operating at high speeds while consuming very little power, said comparator circuit comprising:
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a first stage accepting a first bit string and a second bit string, said first stage generating a first output, said first output comprising a plurality of voltages corresponding to an XOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string, said first stage also generating a second output, said second output comprising a plurality of voltages corresponding to an XNOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string; and a second stage comprising a hit-miss detection circuit, said hit-miss detection circuit comprising a hit line and a miss line, said hit-miss detection circuit further comprising NMOS transistors having NMOS transistor gates and PMOS transistors having PMOS transistor gates, each of said NMOS transistor gates and each of said PMOS transistor gates being controlled by each of said first plurality of voltages and each of said second plurality of voltages respectively, said NMOS transistors being connected in parallel to each other and said PMOS transistors being connected in parallel to each other such that when any one of said NMOS transistor gates goes high and any one of said PMOS transistor gates goes low, said hit line is pulled down and said miss line is pulled up. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A computer system comprising:
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a memory for storage of information; a processor coupled to said memory for manipulation of said information; said processor including a comparator circuit; said comparator circuit comprising a first stage accepting a first bit string and a second bit string, said first stage generating a first output, said first output comprising a first plurality of voltages corresponding to an XOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string, said first stage also generating a second output, said second output comprising a second plurality of voltages corresponding to an XNOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string; and said comparator circuit additionally including a second stage, said second stage comprising a hit-miss detection circuit, said hit-miss detection circuit comprising a hit line and a miss line, said hit-miss detection circuit further comprising NMOS transistors having NMOS transistor gates and PMOS transistors having PMOS transistor gates, each of said NMOS transistor gates and each of said PMOS transistor gates being controlled by voltages corresponding to each of said first plurality of voltages and each of said second plurality of voltages respectively, said NMOS transistors being connected in parallel to each other and said PMOS transistors being connected in parallel to each other such that when any one of said NMOS transistor gates goes high and any one of said PMOS transistor gates goes low, said hit line is pulled down and said miss line is pulled up. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of comparing a first bit string to a second bit string to determine if they are the same, said method comprising:
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generating a first plurality of voltages corresponding to an XOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string; generating a second plurality of voltages corresponding to an XNOR function applied to at least a portion of said first bit string and an equivalent portion of said second bit string; and generating a hit signal and a miss signal on a hit line and a miss line, respectively, by controlling each of a plurality of gates of a plurality of NMOS transistors using each of said first plurality of voltages and controlling each of a plurality of gates of a plurality of PMOS transistors using each of said second plurality of voltages, said plurality of NMOS transistors being connected in parallel to each other and said plurality of PMOS transistors being connected in parallel to each other such that when any one of said NMOS transistor gates goes high and any one of said PMOS transistor gates goes low, said hit line is pulled down and said miss line is pulled up.
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Specification