HP Compaq dc71 Series, Technical Reference Manual

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Technical Reference Guide 361834-002 C-1
C
Keyboard
C.1 Introduction
This appendix describes the HP keyboard that is included as standard with the system unit. The
keyboard complies with the industry-standard classification of an “enhanced keyboard” and
includes a separate cursor control key cluster, twelve “function” keys, and enhanced
programmability for additional functions.
This appendix covers the following keyboard types:
■
Standard enhanced keyboard.
■
Space-Saver Windows-version keyboard featuring additional keys for specific support of the
Windows operating system.
■
Easy Access keyboard with additional buttons for internet accessibility functions.
Only one type of keyboard is supplied with each system. Other types may be available as an
option.
✎
This appendix discusses only the keyboard unit. The keyboard interface is a function of the
system unit and is discussed in Chapter 5, Input/Output Interfaces.
C.2 Keystroke Processing
A functional block diagram of the keystroke processing elements is shown in Figure C-1. Power
(+5 VDC) is obtained from the system through the PS/2-type interface. The keyboard uses a
Z86C14 (or equivalent) microprocessor. The Z86C14 scans the key matrix drivers every 10 ms
for pressed keys while at the same time monitoring communications with the keyboard interface
of the system unit. When a key is pressed, a Make code is generated. A Break code is generated
when the key is released. The Make and Break codes are collectively referred to as scan codes.
All keys generate Make and Break codes with the exception of the Pause key, which generates a
Make code only.