HP-IL
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "HP-IL".

The HP-IL (Hewlett-Packard Interface Loop) was a short-range interconnection bus or network introduced by Hewlett-Packard in the early 1980s. It enabled several devices such as printers, floppy disk drives, tape readers, etc. to be connected to programmable calculators such as the HP-41C, HP-71B and HP-75C/D, the 80-series and HP-110 computers, as well as generic ISA bus based PCs.

Principles

The HP-IL can be seen as a precursor to the Universal Serial Bus now largely in use on desktop computers. However, as its name implies, the cable formed a loop: the cable originated in the HP-IL extension module, ran through all connected devices, then came back to the module.

On the bus, devices could act as controllers (the calculators/computers) or slaves (the peripherals). Certain controllers like the HP-71 module or the HP82973A ISA interface could act as slaves as well, enabling a small network of calculators to be set up.

The IL used a form of Token passing protocol for media access control.

Every device on the bus has a ring-in and a ring-out connector, either on pigtails or built in. HP used a proprietary two-pin connector design with polarizing "D"-shaped shells. HP-IL cables can be interconnected without further adapters to extend their length.

Applications

Hewlett-Packard developed a range of devices to be connected to the HP-IL, mostly peripherals such as printers and storage devices for calculators. Through the 82169A HP-IL/HP-IB Interface, HP-IL controllers could be connected to instruments with an HP-IB (aka GPIB or IEEE-488) interface, or vice versa. There were also plans to make test equipment with IL interfaces, but apart from the somewhat popular 3468A multimeter, only a few devices were introduced before HP-IL itself became obsolete.

In addition to the HP-IB interface, HP also sold RS-232 and general-purpose parallel I/O interfaces as well as a prototype kit to create custom interfaces.

Equipment with HP-IL Interface

Controllers

• HP 82160A HP-IL Module for the HP-41C
• HP 82973A HP-IL interface for IBM PC and compatibles with ISA bus
• HP 82938A Interface for Series 80 desktop computers/controllers
• HP 82401A HP-IL module for HP-71B
• HP-75C/D
• HP-110
• HP-150

Interfaces

• HP 82164A HP-IL/RS-232C Interface (serial port)
• HP 82165A HP-IL/GPIO Interface (generic parallel port)
• HP 82166A HP-IL Converter (smaller version of GPIO interface intended for embedded use)
• HP 82166C HP-IL Converter Prototyping Kit
• HP 82169A HP-IL/HPIB Interface (bidirectional)

Peripherals

• HP 9114A/B Disc Drives
• HP 82161A Tape Drive
• HP 82162A Thermal Printer (HP-IL version of HP 82143A printer for HP-41C)
• HP 82163A Video Interface
• HP 92198A 80-Column Video Interface (Mountain Computer)
• HP 82168A, 92205M Acoustic Couplers (Modems)
• HP 82905A/B Printers
• HP 2225B ThinkJet Printer
• HP 7470A Graphics Plotter (Opt. 003 HPIL Interface)
• HP 2671A/G Alphanumeric Graphics Thermal Printer

Test instruments

• HP 1630 and HP1631 Logic analyzers (can be loop controller)
• HP 3421A Data Acquisition/Control Unit
• HP 3468A/B Digital Multimeters (HP-IL version of HP 3478A with GPIB)
• HP 5384A and HP 5385A frequency counters with option 003 (HP-IL)

Software

• HP-IL Development Module (plug-in Application ROM module for HP-41C)
• HP 82183A Extended I/O Module

Third-party

• FSI164A HP-IL/RS-232C Interface
• Leitz IL-41 Theodolite interface

References

• Gerry Kane, Steve Harper, David Ushijima: THE HP-IL SYSTEM: An Introductory Guide to the Hewlett-Packard Interface Loop. ISBN 0-931988-77-2
• HP Journal, January 1983 (Several articles about HP-IL and related products)
• HP 82160A HP-IL Module Owner's Manual for the HP-41
• HP 82401A HP-IL Interface Owner's Manual for the HP-71

See also

• IEEE-488 (GPIB,HPIB)
• Apple Desktop Bus
• Universal Serial Bus

External links

• http://www.hpmuseum.org
• http://www.hp41.org/HPIL.cfm
• http://www.hp-collection.org/hpil.html