Celebrating 30 Years of PLCIO
With version 1 written in 1991, PLCIO has proven to be intregal to operators needing robust PLC library communications. Bill Hays, original vision behind PLCIO, shared his story of the creation of PLCIO in 2016, it's 25th anniversary.
I was asked about the lineage of PLCIO – how did it get to be the product it is today?. Today’s PLCIO is much different that the earliest versions, but 25 years ago the Intel 386 processors were mostly being used as a way for 16-bit DOS to access bigger memory models, so much has changed!

PLCIO was born from the need to provide a simple, but effective communications interface to talk to I/O devices. Our primary objective was to abstract the application and communications layers so that someone programming the business and database logic would not have to worry about the communication details.

In 1991, CTI (Commercial Timesharing Inc.) created the first version of PLCIO for HP-UX 7.0 UNIX systems to communicate with Allen Bradley DF1 (a serial protocol). A simple Modbus protocol addition was not far behind. Also at this time the Intel 386 processor made possible new UNIX operating systems for microprocessor platforms. These included SCO UNIX and Interactive UNIX (by Kodak).

We were looking for a factory automation solution for placing UNIX systems on the factory floor. We signed a license agreement with Interactive UNIX and created our own CCWS UNIX (Cell Controller Work Station) so that we could place multi-tasking systems with full network capability in the factory. Two key technologies to come out of that effort were: 1) the ability to boot diskless (using BOOTP protocol), and 2) drivers for the SA-85 card (Modbus+ ISA card) and AB-KT card (Data Highway + ISA card).

As we developed these systems we quickly identified the need to support unsolicited message-based communications. The end result -- a multi-tasking OS that could receive, process, and send response messages – allowed CTI to be successful and very competitive in the design and deployment of complex material handling and other process-controlling tasks.

Within a few years, CTI was contracted to implement a couple of key protocols for GE Fanuc’s CIMPLICITY product. Pieces of PLCIO technologies were integrated into the devcom elements and this product was used until the ISA bus was finally retired.

Getting the word out about PLCIO to the programmers who needed it was a struggle in the beginning, being limited to some magazine and trade journal ads. However, there were early adopters of UNIX for whom these protocols were very useful.

The next major release of PLCIO didn’t come until 1998, when CTI started working with a young/risky/new operating system called Linux. The PLC market was changing, and Ethernet equipped devices were becoming more widely available. Following the rise and fall of the market, PLCIO started to use Modicon Ethernet, Allen Bradley CIP (using the CELL library), and other niche protocols. The PCI bus had pretty much replaced ISA, and some of the legacy ISA implementations were creating driver challenges as well.

As development and use of the Internet exploded, CTI began to market PLCIO on the web as part of the company’s software and integration offerings. A section of the web site was dedicated to PLC communications and PLCIO. But it would not be until 2007 that PLCIO was given its own “stand alone” domain and web site.

Windows (as a factory/MMI platform) was becoming more popular by 2000, and OPC was gaining in popularity. PLC manufacturers started to abandon what little UNIX platform support they had, which was unfortunate because new PLCs were more commonly Ethernet-equipped and for the first time could easily communicate with larger computer systems. Many UNIX projects developed at that time needed to bridge through a Windows/OPC computer to fetch production data, which often resulted in complex and fragile implementations. PLC Manufacturers don’t always understand that large “Big Iron” systems are a reality for many corporations, and Microsoft doesn’t always meet these technical needs.

By 2003, the PLCIO CIP protocol using the CELL library was no longer meeting our business needs (performance, compatibility, and 32/64 bit platform issues). While I had originally implemented the library after spending time with the open source CELL project (thanks Ron Gage for giving me a foothold on this complex protocol—I owe you a steak!), it was time to tap our resident Linux systems guru Byron Stanoszek as the lead engineer tasked with revising CIP protocol implementation. As PLCIO started to flourish under Byron’s direction, I was able to spend more time directing the sales and marketing of the PLCIO line.

Byron’s significant improvements and restructuring brought about PLCIO 4.0. Implementation of the CIP protocol became blazingly fast and Siemens Ethernet protocol was added to the ever growing list of supported equipment. Byron now heads a growing team of software engineers who continue to develop and support PLCIO, ensuring its relevance far into the future.

(And yes, we still support DF1.)

William Hays
Commercial Timesharing Inc.

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