Device
Controller
A block
diagram
of
a typical device controller is shown in
Figure
3-29.
J
Regulator
+5
Volts
1
-I
+12V
I
+12V
GND
1
GND
HP-HIL
Data
HP-HIL
Data
SI
so
RO
RI
HP-HIL
Data
HP-HIL
Data
Device
Interface
;t
1\
\J v
Device
Micro-
processor
Device-Specific
.t1
1\
Components
N
V
Figure 3-29. HP-HIL Device Controller Block Diagram
Regulator
From
the
HP-HIL cable,
+12
Vdc is regulated down
to
+5Vdc
for use by device components.
The
+
12
V dc
input
is
also sent
to
components
needing
that
supply.
Device Interface
The
device interface serves as
the
communication link between
the
device
and
system
HP-HIL
microprocessor. In
addition
to
transmitting
and
receiving
data,
it also
interrupts
the
device
microprocessor when a correctly addressed
data
frame
or
improper
fonnat
is
received.
It
also
provides device
hardware
reset, lowers
the
NMI line
at
power-up
and
at
device
hard
reset
con1mand.
Device Microprocessor
Tasks performed by
the
device microprocessor include
maintaining
the
interface,
data
sending
and
receiving tasks.
It
also converts device information
to
data
for
the
device microprocessor
to
send
to
the
computer
as
human
input
information.
Device-Specific Components
Various
components
are
used depending
on
the
device. Digitizers, keyboards, knobs,
and
a host
of
other
human
input
functions are converted
to
data
for
the
device microprocessor. Each device
will have
its
own specific components, depending on
the
input
task
details.
112
Functional Description
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