HP-IL technical info request


I'm after some information about HP-IL at the electrical level.

I understand that the book "The HP-IL System: An introductory guide to the Hewlett Packard Interface Loop" by G Kane, S Harper and D Ushijima may have the information I'm after.

Does anyone have a copy?

Does anyone have any other source of information about the electrical and signal characteristics of the HPIL?

Does the IL Development ROM manual have any information?


I have a copy of that book. It does contain an overview of HPIL workings, some state diagrams, and brief electrical details. It also states that it's not intended to replace a document called 'HP-IL reference specification' - this is apparently what you should use if you want to implement the HP-IL.

It might just be possible to reverse-engineer a working HP-IL setup with this book as a guide.


The HP-IL Interface Specification has been scanned for inclusion on a future museum CD (probably a month or two away.) Send me an email if you need an early copy.


"It might just be possible to reverse-engineer a working HP-IL setup with this book as a guide."

That's sort of what I'm trying to do.

I've discovered that OUTP (from the Extended I/O module) can be used to just send a program out onto the loop. This works without anything being on the loop.

Unfortunatly the transitions are too fast to be captured on a sound card (I just get some transitions and ringing). From memory The IL operates at around 100KHz, so I need to sample at 200K samples/second which is way faster than a sound card can do.

I'm hoping to figure out a cheap way to interface IL with a PC. If INP works anyway like OUTP (although I doubt it) there is a chance that bidirectional transfer could be set up without having to go the whole hog in implimenting HPIL.


I guess it's easier to implement it in a microcontroller (the basic functions) and to interface this uC to a PC. I believe, that a PC is not fast enough with its interrupt response, so you could lose frames without a dedicated device. Remember, that you must retransmit every frame.

I planned to do such a thing years ago, but there was no time til now (and I'm sure there will be no time for the next months :-( )

I'd take the PIC uC series because I know the PICs well, but I believe, there would be no problem in using another uC, if it's fast enough.

You can have any help, if you get in trouble with this project


Reinhard Hawel wrote:

>I guess it's easier to implement it in a microcontroller >(the basic functions) and to interface this uC to a PC.

The only reasonable way to accomplish such a project is to design the interface around the HP 1LB3-0003 chip; it is rather difficult otherwise, given the electrical characteristics (such as the bit/asynchronous nature of the frame, meaning that not only the timing between frames is allowed to vary but also the timing between bits inside a frame) and the complex state transition diagram for the functions that the interface is expected to execute in real time (too fast for interrupts).

You can rip 1LB3-0003 chips off most HPIL devices that HP made. The documentation booklet is "The HP-IL Integrated Circuit", HP doc 82166-90016 Rev. B. The first paragraph in the introduction states that "This document describes the 1LB3-0003 HP-IL integrated circuit and is intended primarily for the designer of an HP-IL device. It presumes a complete understanding of the document entitled `The HP-IL Interface Specification' (82166-90017) which defines the functional, electrical and mechanical aspects of the interface system'.

I've been wanting to implement an HP-IL digitizing/control unit based on the 68HC11 and the 1LB3-0003 chip for a while. I've found it easier to hunt the documents and chips than the time to actually do the thing :-( .


I've just bought myself a PIC programmer. I'm planning to have a play with these devices to learn more of what they can do.

I've found that you can get away with NOT retransmitting every frame if your aim is simply to eavesdrop on the HP-IL interface. (eavesdropping is OK to intercept the OUTP which seems to just blast the program out onto the loop (presumably for some listener to intercept and read).

The main trick is determining exactly what is the format of these frames and the electrical specification of them on the IL bus so that I can interface them to the PIC.

It will be a while until I'm in a position to look at this.



There are a LOT more documents about HP-IL that are available. The BEST source is one of the HP 82166C kits. It was a kit of parts intended for use in designing HP-IL into other devices. It contained most of the parts to built two HP-IL interfaces (HP 82166As) and ALL of the available HP-IL documentation along with a good supply of developer's tools such as HP-IL Development modules for the HP 41. I have one of the kits and here is a list of what's in it. I wrote list for something else so it's not formated for this page and it contains unrelated info.


Contents of the HP 82166 C HP-IL Interface Kit

Manuals and Media

RIOWIO Instruction Card, 2 pg. , 00075-90144 ESD Caution Card, 1 pg., 82166-90013 HP-IL Application Note Firmware Design for HP-IL Devices, 82166-90024 HP 82166C The HP-IL Interface Kit Technical Guide, P/N 82166-90020 Rev B, May 1983 HP 82166A HP-IL Converter Technical Manual, 33 pg., P/N 82166-90002, Nov. 1982 The HP-IL Interface Specification, P/N 82166-90017, Nov. 1982 The HP-IL Integrated Circuit User's Manual, P/N 82166-90016 Rev B, Nov. 1983 HP 00041-15043 HP-IL Development Module Owner's Manual, P/N 00041-90449 Rev B, Oct. 1984 HP 82165A HP-IL/GPIO Interface HP 81266A HP-IL Converter Manual Supplement P/N 82165-90012, Oct. 1982 *** Bound manual. I have another of these dated 1982 that is not bound.. HP-75 User’s Library Solutions I/O Solutions, 47 pg., 00075-90122 THE HP-IL SYSTEM: An Introductory Guide to the Hewlett-Packard Interface Loop; Gerry Kane, Steve Harper and David Ushijima, 105 pg., ISBN 0-931988-77-2

One tube of HP-75 magnetic cards labeled “Hewlett-Packard RIOWIO”, 00075-12025 One tube of HP-75 magnetic cards labeled “Hewlett-Packard I/O Utilities”, 00075-12022


One short tube containing 4 HP-IL pulse transformers P/N 9100-4226 Four plastic bags each containing 1 HP-IL panel receptacle P/N 0950-0852 One plastic tube containing 4 HP-IL Integrated Circuits P/N 1LB3-0003 AND 2 Micro Processor Integrated Circuit P/N 1820-2810 One plastic bag containing 8 #2 self-tapping screws and washers P/N 0624-0302 and 3050-0626 One plastic bag containing 8 15K Ohm 5% .25 Watt Resistors P/N 0683-1535 One plastic bag containing 8 383 Ohm 1% .25 Watt Resistors P/N 0698-3446 One plastic bag containing 4 .1 Micro Farad Capacitors P/N 0160-0576 One plastic bag containing 4 120 Pica Farad 5% Capacitors P/N 0160-4800 One plastic bag containing 4 56 Micro Henry 5% Inductors P/N 9100-1631 One plastic bag containing 8 1N973B Zener Diodes P/N 1902-0970 One plastic bag containing 8 6.2 Volt 1N753A Zener Diodes P/N 1902-0953 One plastic bag containing 2 4 MHz Crystals P/N 0410-1305 One plastic bag containing 8 330 Pica Farad 5% Capacitors P/N 0160-4292 One plastic bag containing 4 10 Micro Farad Capacitors P/N 0180-3135

Note: The manual says that kits assembled after the second quarter of 1983 should include 4 HP-IL hybrid networks P/N 1810-0651 instead of some of the separate components. I have one kit with separate components and another with the hybrid parts.

Note: The manual says that the microprocessors are included so that the builder has the option of building an interface which duplicates the function of the 82166A HP-IL Converter. Note, that although there are enough parts to build four interfaces, there are only two microprocessors and no cases or circuit boards.

Two plastic bags each containing 1 HP-41 HP-IL Development Module

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