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Browse Prior Art Database

Interface of a Low-Power Keyboard for Lap-Top Computers

IP.com Disclosure Number: IPCOM000102066D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Ballou, RV: AUTHOR [+3]

Abstract

This article describes a technique and hardware implementation to reduce power on a computer keyboard by stopping the scanning for keys with a signal from the system software.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Interface of a Low-Power Keyboard for Lap-Top Computers

       This article describes a technique and hardware
implementation to reduce power on a computer keyboard by stopping the
scanning for keys with a signal from the system software.

      The keyboard controller should be implemented with either a
static chip whose clock can be stopped without loss of state, or with
a chip that provides a power-down mode.  A line from the system
called -PWRUPKB shall be monitored by the keyboard.  When the line is
active (less than .8 volt), the keyboard shall be active and scanning
for key depressions.  When the line level goes high (greater than 3.0
volts), the keyboard logic will enter a standby mode where a minimum
amount of power is being drawn. Furthermore, if the keyboard is in
standby mode and the WAKE-UP key is pressed, the keyboard shall exit
standby mode and begin scanning before any other key can be pressed
to ensure that no key depressions are ignored.  In this case, the
keyboard shall not enter standby again until the -PWRUPKB line has
gone active (low) and then inactive (high) again.

      The -PWRUPKB line will be toggled by the system software based
on its determination of system activity. This determination can be
made by using an activity monitor circuit.

      The keyboard will have a key that will not be included in the
scanning matrix.  It shall instead be implemented with a circuit
equivalent to the one shown in Fig. 1.  Fig. 2 shows th...