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Browse Prior Art Database

Keyboard/Digitizer/Power Management Service Processor

IP.com Disclosure Number: IPCOM000106512D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 6 page(s) / 242K

Publishing Venue

IBM

Related People

Leontiades, K: AUTHOR [+2]

Abstract

Described is a hardware and software implementation that combines keyboard, digitizer and power management interface control into a single low power micro-controller. The implementation is particularly useful in portable pen based computers where size is critical.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 26% of the total text.

Keyboard/Digitizer/Power Management Service Processor

      Described is a hardware and software implementation that
combines keyboard, digitizer and power management interface control
into a single low power micro-controller.  The implementation is
particularly useful in portable pen based computers where size is
critical.

      In portable computer systems, it is considered essential to
minimize the number of components because of space and power
constraints.  Typically, pen based systems are required to control
digitizers, to manage power, and to control optional keyboards.  In
prior art, one or two micro-controllers were added to control these
devices.  This required additional increases in space and power for
environments which dictates a low profile.

      The concept described herein provides a means whereby a
controller relieves the main processor from excessive device
interrupt processing by receiving, buffering and preliminary
processing of data.  A single controller is used to control the
keyboard, digitizer and power sub-system of a pen based computer.
The single controller is a service processor (SP) that interfaces
with the system in three areas; a) through the standard keyboard
controller interface that is modified to support the digitizer and
the power subsystem; b) interfaces with the stylus/digitizer over an
interrupt driven serial interface and; c) interfaces with the power
subsystem over a polled serial interface, similar to the keyboard
interface.

      In actual operation, the SP off-loads from the main system
processor much of the input/output (I/O) intensive processing needed
to manage the keyboard, digitizer, and power subsystem interfaces.
In addition, the SP assists the main system processor with power
management and supervises the system while the main processor is not
operational.  The SPs main functions are as follows:

o   Keyboard Control - The SP receives keyboard scan codes over a
    serial polled interface and after optional translation passes the
    codes to the system.  The SP also transmits system commands
    directly to the keyboard and sends keyboard replies back to the
    system.

o   Power Subsystem Control - The SP receives power subsystem status
    information from the power subsystem microprocessor over a serial
    polled interface and passes this information to the system after
    appropriate interpretation.

o   Digitizer Control - The SP receives and buffers digitizer
    coordinates over a serial interrupt driven interface at a high
    rate of speed and passes them on to the host after appropriate
    processing as defined by the host by way of configuration
    commands.

o   Contrast/Brightness Control - The SP monitors the four contrast
    brightness switches and adjusts the liquid crystal display (LCD)
    contrast and brightness accordingly.

      Fig. 1 shows a block diagram of the SP as it resides on the
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