I have another question I hope can be answered(even if it seems stupid, I need validation for my research paper so please bear with me :) )

If the hardware RTC in a PLC rolls over to 01/01/1900 and the software RTC rolls over to 01/01/2000, would this cause the PLC to crash because the two dates are in conflict? If date conflict causes the PLC to crash, how much of a difference? Does a difference of a month, a few days, or even minutes matter?

Also, if a PLC and a SCADA has a conflicting date, will this cause the SCADA to shut down the PLC?

-Ben Gibbs

-- Anonymous, November 28, 1998

Answers

I know that some current-year production PCs have experienced problems with having perfectly up-to-date software but non-compliant RTC chips. The software runs fine until you have to reboot the computer whereupon you discover that your machine won't reboot. I'm not sure how the condition would affect non-"Wintel" machines but I can see a few scenarios where the system accesses the hardware RTC as a reference and gets date data that makes NO sense whatsoever to the application. Hope this helped. Keith

-- Anonymous, November 29, 1998

Ben, here's some more info that you might find useful for your paper. It's not directly related to the electric power industry but it will give you some idea of the problems and stats for a large plant.

Scroll down to the "Case Study" section.

http://www.tmn.com/~frautsch/cargill.txt

Regards, --AJ

-- Anonymous, November 29, 1998

Ah, thanks for clarification, this board has been a big help =)

-Ben

-- Anonymous, November 30, 1998