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.

Contents

Principles

Applications

Equipment with HP-IL Interface

Controllers

Interfaces

Peripherals

Test instruments

Software

Third-party

References

External links

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 be acting 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/HPIB Interface, HP-IL controllers could be connected to instruments with an IEEE-488 (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

External links

★ http://www.hpmuseum.org

★ http://www.hp41.org/HPIL.cfm

★ http://www.hp-collection.org/hpil.html