Miscellaneous active electrical nonlinear devices – circuits – and – Gating – Converging with plural inputs and single output
Reexamination Certificate
1999-12-21
2002-04-09
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Gating
Converging with plural inputs and single output
C327S099000, C327S100000, C327S408000
Reexamination Certificate
active
06369636
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to calibrating circuits generally and, more particularly, to a method, architecture and circuit for selecting, calibrating and monitoring a plurality of circuits.
BACKGROUND OF THE INVENTION
A conventional approach to calibrating circuits is to (i) calibrate a single buffer during chip power-up and (ii) program any remaining buffers to that calibrated value. An example of this approach is the “Programmable Output Impedance Circuit” used by the 1302 PAQ SRAM chip, the data sheet of which is hereby incorporated by reference in its entirety.
Because the 1302 PAQ SRAM chip has output buffers located on opposite sides of the chip die, a single cycle calibration approach does not accurately account for process times of uncalibrated outputs located away from the calibrated output. As a result, the conventional calibration approach produces a mismatch in process times introducing an error of +/−5% or more.
SUMMARY OF THE INVENTION
The present invention concerns a circuit comprising a plurality of first calibration circuits, a second circuit and a third circuit. The plurality of calibration circuits may each be configured to present a calibration signal. The second circuit may be configured to select one of the calibration signals in response to a plurality of configuration signals. The third circuit may be configured to generate a control signal in response to (i) a reference signal and (ii) the selected calibration signal.
The objects, features and advantages of the present invention include providing a circuit that may (i) calibrate a plurality of circuits, (ii) monitor the calibration of a plurality of circuits and/or (iii) continuously monitor and calibrate a plurality of circuits.
REFERENCES:
patent: 5015970 (1991-05-01), Williams et al.
patent: 5081705 (1992-01-01), Swanke
patent: 5130565 (1992-07-01), Girmay
patent: 5703489 (1997-12-01), Kuroe
patent: 5952888 (1999-09-01), Scott
Cypress Data Communication Data Book, CY7B951, Local Area Network ATM Transceiver, 1996, pp. 3-1 to 3-8.
Cypress Data Communications Data Book, CY7B952 SONET/SDH Serial Transceiver, 1996, pp. 3-9 to 3-15.
Cypress Data Communications Data Book, CY7B923 CY7B933, Transmitter/Receiver, 1996, pp. 4-1 to 4-27.
Practical Data Communications by Roger L. Freeman, 1995, pp. 130 to 286; John Wiley & Sons, Inc.
Cypress CY7C955, AX™ ATM-SONET/SDH Transceiver, Jul. 1997, pp. 2 to 76.
Christopher P. Maiorana P.C.
Cypress Semiconductor Corp.
Wells Kenneth B.
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