HARDWARE
A
thumbwheel
control
on
the
right
hand
side of
the
Keyboard
Unit
adjusts
the
viewing angle of
the
MicroScreen.
The
MicroScreen
can
be used
in
a variety of applications;
e.g. for displaying:
(a)
A real
time
clock,consisting of
the
time,
the
day and
the
date.
(b)
Labels for
the
six
'soft'
function
keys.
(c)
A copy of
the
data
as
it
appears
on
the
CRT
display.
(d)
System
prompts.
(e)
Operands
and
results
during calculator operations.
The
electronic
circuitry
of
the
Keyboard
Unit
is contained
on
a single
printed
circuit
board fitted
horizontally
within
the
Keyboard
Unit
housing. A block diagram of
the
keyboard
circuitry
is
shown
on
Figure 2a/2b.
All
the
keys are of a capacitive type
with
keyboard
scanning performed
using
a single chip microcomputer.
The
microcomputer
translates
the
selected
key
switch
into
a
scan code,
which
is transferred to
the
System
Unit
via
the
serial link.
The
use
of
scan
codes enables application
programs to redefine
the
code (or sequences of codes)
generated by
the
system, as required.
All
communication
between
the
Keyboard
and
the
System
Unit
is
handled
by
the
microcomputer
within
the
Keyboard. In
addition
to
transmitting
the
keyboard scan
codes to
the
System
Unit,
the
microcomputer
also provides
the
System
Unit
with
the
following serial data:
(a)
Current
time
and
date
information
on
request
from
the
System
Unit.
(b)
Control
codes generated
by
the
movement
of a
"mouse"
device,
when
connected
to
the
Keyboard
mouse
port.
The
time
and
date
information
is generated by a real
time
clock/calendar chip
on
the
Keyboard
circuit
board. A
battery (standard PP3) back-up supply is
connected
to
the
clock/calendar
to
allow
it
to
continue
functioning
when
the
mains
supply
is
switched
off.
To Next Page
Loading...
