DR. JOHN ROBERT LEWIS, OD
Optometry at Fremont St, Portland, OR

4908621, Mar 13, 1990

Jul 6, 1988

7/215667

John D. Polonio - Beaverton OR
Bruce J. Penney - Portland OR
John Lewis - Tigard OR

Tektronix, Inc. - Beaverton OR

H03M 106

341120

An autocalibrated multistage analog to digital converter precisely maintains appropriate error correction levels for each stage during operation of the converter to minimize quantization errors. An error signal is derived from the digital output of the converter based upon the slope of the input analog signal, determined either explicitly via hardware or implicitly via software, and an overflow/underflow condition. The error signal is fed back to a calibration control circuit to generate individual error correction levels for various variable correction devices within the analog to digital converter, such as a variable analog delay device. The variations from nominal established at calibration that are due to age, temperature or other environmental factors generate the error signal that varies from a nominal value and is fed back to alter the various error correction levels to minimize the error variation.

4393443, Jul 12, 1983

May 20, 1980

6/151541

John Lewis - Tigard OR

Tektronix, Inc. - Beaverton OR

G06F 936

364200

A circuit for enhancing the performance of a random-access-memory-based memory expansion system is disclosed. Memory capacity and a control register are added to the traditional memory mapping circuit. The increased memory is utilized to store several maps simultaneously and the circuit output is then switched from one stored map to another according to data present at the control register outputs. Thus, by pre-loading the circuit with all the memory maps required by a particular program, delay caused by map changes is reduced to the time required to move data to the control register outputs.