United States Patent 4,109,315
Wristwatch Calculator with Selectively Scanned Keyboard
Aug. 22, 1978
Inventor: Michael Pan, San Jose, Calif.
Assignee: Hewlett-Packard Company, Palo Alto, Calif.
Appl. No.: 718,741
Filed: Aug. 30, 1976
Abstract:
A wristwatch calculator is provided with a keyboard for the entry of
information into and control of operation of the apparatus. The keyboard
comprises an array of switches connected in an X-Y matrix that is scanned by
row and column to find and identify a key that has been depressed. The
scanner is operated only when the calculator circuitry in the apparatus is in
a sleep or inactive mode in order to save battery power.
1 Claim, 8 Drawing Figures
An image of first page of this patent is
available (approximately 35 Kbytes).
It is a TIFF class F file at 300 DPI resolution using ITU-T Group 4 Facsimile
(T.6) coding.
Eric's notes:
This patent describes the keyboard scanning circuitry of the HP-01. The
approach to saving battery power described in this patent seems to be less
than ideal even for mid-70s technology. A more typical approach would be to
drive all of the key scan lines active while in sleep mode, and return to
"waking" mode and activate the key scanning when any key return line become
active.
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Last updated July 17, 1995
Copyright 1995 Eric Smith
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