HP 330 Service Information Manual page 125

HP-HIL Devices
Introduction
Hewlett-Packard HUlllan Interface Link (HP-HIL) is an HP standard for interfacing Series 300
computers and other workstations to human input devices. A list of HP-HIL devices is shown
in Table
~~-11.
Asynchronous serial communications protocol enables you to select a set of input devices, con-
nect thern to your computer, and work with any application program.
A link controller on the system interface board controls the HP-HIL. Each HP-HIL device has
an circuit to interface information to and from the device. Limitations for the HP-HIL are:
• Up to seven devices can be on the link.
• Maximum distance between devices is 2.4 metres, total link maximum length is 16.8
metres. This does not include the 15 or 30 metre extensions.
• Series 300 Maximum link current is 1 A.
Link Controller
A block diagram of a typical link controller is shown in Figure 3-26.
I
Power
I
+12V
Supply J
GND
HP-HIL Data
so
51
HP-HIL Data
Computer
Unk
Interface
J1 1\
\I V
Sy.tem
Micro-
I
~
1\
proc:enor
System-Specific
Components
'\I
V
Figure 3-26. HP-HIL Link Controller Block Diagram
Power Supply
One voltage, +12 Vdc is taken from the host computer and output as a regulated power supply
to external devices on the link. Up to 1 A can be supplied to devices. When configuring HP-HIL
devices with Series 300 computers, care must be used to ensure the total power drawn by all
devices does not exceed 1 A. In Table 3-11, devices are listed with their power requirements.
Functional Description
109