HP 330 Service Information Manual page 128

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