TechArchive

Original article date: May 1998

Are my manufacturing hardware and software systems Year 2000 compliant? This question is being asked in board rooms in purchasing offices and on the plant floor. Unfortunately there is no simple answer to this question. What can be done?

During 1995 more than 200 million personal computers were sold world-wide. Yet in 1996 the number of embedded systems distributed was around 7 billion. So is the year 2000 issue a problem for micro PLCs? The answer has to be: it depends on the application! If we assume that Micro PLCs tend not to have built in diagnostic features based on a time schedule and we assume the user has no program or function derived from a real time clock and calendar (RTC/RTCC) then no there is no problem. This tends to be the case in very many applications and most suppliers of PLCs appear content to leave it there. Not much advice though from many of them on what to do about existing applications.

And there are, says Chris Hazlewood from Mitsubishi, products with real time clock-calendar (RTCC) facilities built in and others which offer this as a product supplement. This highlights the need to identify where the RTCC function are within any given piece of micro electronics or Micro PLC. However judging by the number of enquiries received by Keyence’s Simon Smith there is no doubt that users take very seriously although Chris Hazelwood says that it won’t mean the end of the world even if as Rockwell’s Richard Sturt suggests the lights go out at midnight 1999!

Like most PLCs and associated software the Keyence range is checked for millennium compliance but the view taken is that this range is unlikely to cause any problems because no real-time clock or embedded date is contained within the processor.

Ian Purcell at Matsushita agrees and points out that the majority of applications performed by PLCs are not real-time dependent and so this issue does not generally present a problem. For applications where RTC is an issue he says that it is up to the application engineer to ensure that application program can cope with the change effectively. If the Micro PLC offers RTC functions and the PLC programmer has utilised these then the PLC programmer should check through the appropriate sections of code. In the case of the RTC in NAiS branded products from Matsushita time information is confined to two digits for hours minutes and seconds. The date information also uses two-digit data for the day month and year and therefore ignores the century information. According to Purcell this ensures that NAiS PLCs are Year 2000 compliant.

Omron’s Paul Downey notes that clock and calendar functions within PLCs are increasingly being used for applications such as error reporting event sequencing and product tracking and this capability is increasingly either an option or a standard even on microcontrollers. All controllers with such functionality should be fully compliant with the Year 2000 issue and all Omron controllers at least with clock and calendar functions have been tested.

Richard Sturt also takes the view that the Year 2000 issue is a problem for micros with real-time clocks but the Rockwell Micrologix does not have one either. The SLC (in versions over 30 I/O) does but it is Y2K compliant. He recognises though that there are hundreds of small controllers knocking around that do have a real-time clock and are not Year 2000 proof. If they are spread throughout a building controlling the lights they will be difficult to identify and fix but if you don’t. says Richard Sturt the lights will go out at midnight 1999!

Chris Hazlewood points out that even if a product does not offer RTCC functions directly to the user they may still exist within the product itself. The manufacturer may use time or calendar functions to help provide maintenance information or perhaps just simple performance statistics. So it is important that customers do not feel afraid to ask the manufacturer for statements regarding the applicability and use of RTCC data in any micro electronic product. Mitsubishi has a statement available on request from any user.

Another issue is that if the Micro PLC is connected back to a master network where some type of SCADA is used not only to monitor/supervise but in 99% of situations actually provide the date and time stamping then there is a very real possibility that the system administrator should look seriously at getting the SCADA package and indeed the computer verified for the extent of compliance with the issues of the year 2000.

Within the Mitsubishi FX family of Micro PLCs the F F1 F2 FX0 and FX0S have no RTC function at all. Customers may be confused and ask “How is it then that your PLC can provide timer operations?”. This is simply explained: the generic timers used in all Mitsubishi FX family of PLCs are actually counters! Instead of receiving external inputs to trigger the count the PLC actually counts pulses output from a quartz crystal. Hence when you see a timer with 100ms duration what you are actually seeing is a counter with a limit of 100 counts of 1ms clock pulse or a 100 0 counts of 0.0001ms.

The Mitsubishi FX0N and FX products also have no RTCC function built in. However a supplementary RTC memory cassette is available. The RTC cassette offers a time period calendar function. In this particular example that is until the year 2079. It is quite a common practice to offer a specific time frame type operation – for example videos typically will only have a 10 or 15 year clock function. Because the time duration is controlled extensive and appropriate testing allows the manufacturer to ensure the RTCC product performs correctly. In the case of the Mitsubishi FX RTC memory cassettes they have been tested to ensure that they recognise both the change to the year 2000 and the recognition that the year 2000 is actually a leap year. So the PLC will recognise and process “time as we know it” correctly.

But as with any other piece of information supplied by the PLC it is subject to the interpretation of the user – or specifically in the case of the PLC – the PLC programmer. Mitsubishi recommends that customers check their own programming to see that they have not created a situation where the original time/calendar data provided by the PLC can be misrepresented.

The latest Micro PLC product from Mitsubishi the FX2N is the first micro PLC the company has produced with the RTC function built in as standard. Mitsubishi has applied the same technology to the new FX2N RTC functions as was available in the existing FX RTC cassettes but with one important difference. To try to remove the possibilities of time/calendar data being misrepresented Mitsubishi has added six special RTCC comparison and handling instructions with an additional but optional function of switching the year data from two-digit to four-digit.

So all PLC suppliers have established policies for identifying which applications are likely to present a problem and to ensure that new PLCs leaving the factory gates are millennium-compliant. In conclusion the user is well advised to seek confirmation from all suppliers of equipment that are used – it only takes a few minutes or a short fax to ask the question but it may save hours of unnecessary rework or facilitate a positive action to resolve the issue.

What about software issues? At Rockwell Software products released as of 1 January 1998 must be year 2000 compliant. Many software products such as the line of ladder logic programming packages and communication products do not use data to perform any of their core functions. Therefore year 2000 compliance is not an issue in those products.

But Dan Woodward of Rockwell Software’s Quality Group points out that though Rockwell does not ship software that could be deactivated by setting the date to 1-1-2000 other software manufacturers may so be sure to test these.

According to Woodward software compliance is only the first step toward removing risk. It is a very important step but software compliance alone is not enough to ensure proper operation in the complex world of control automation. There are many elements that make up an industrial automation solution. The particular personal computer you use to run the software the way the application is designed and many other factors can all play a part in year 2000 compliance. Don’t stop checking just because you have the right releases of software.

Woodward says that one important element in an industrial automation project is the personal computer you use to run your software. Most PCs made before 1995 have problems with their Basic Input/Output System (BIOS). Systems with a BIOS problem do not perform the rollover to 2000 properly. These machines flip back to January 1980. This happens behind the scenes and a DOS DATE command does not show the problem until you power down the computer and power it back up. Some software products rely on the PC BIOS for the current system time.

Most Pentium computers do not have a problem with BIOS but do not assume this. To test for a BIOS problem it is best to use a non-production system that is of the same make model and generation. Set the date to 1-1-2000 and observe system functions. On many newer post-1993 systems you can upgrade the BIOS via software. Other systems require an updated BIOS chip.

After verifying the compliance of the software processors and computer look at other aspects. Ask the following questions:

• Is the application getting date information from any external source?
• Is it providing coded information to an external device or package?
• Is it using internal logic that is based on a special encoding method?

Finally look at the connections in your process and look for weak links based on dates. They may be there hiding behind a thumbwheel on a control panel or in a connection to a UNIX mainframe upstream from your actual process!

• The Government’s Millennium Bug Campaign Action 2000 has released a 16 -page Embedded Systems Guide. The document contains a step-by-step guide to carrying out a Year 2000 embedded systems investigation and recommends various plans of action for finding solutions. It also suggests appropriate questions that product users can ask of suppliers and manufacturers in order to establish the compliance status of a system of component. Copies of the guide can be obtained from Action 2000,

Action 2000:http://www.open.go v.uk/bug2000.htm

Submissions from the following companies are gratefully acknowledged

• Keyence
• Matsushita
• Mitsubishi
• Omron
• Rockwell

May 1998