Embedded Systems Clarificationgreenspun.com : LUSENET : TimeBomb 2000 (Y2000) : One Thread
Here is an exerpt from an email that was passed on to me some time ago, regarding embedded systems. Funny how these fires and explosions keep popping up.
--begin-- First embedded systems do not have a standardization program in place. In essence there can be several ways programs are written. Now to the Y2K question. There are buffers in most embedded system programs. This buffers can be varying in size. When a command is registered with an embedded system and it is improper or not accepted it can place the command in the buffer. It could be doing this by the hour, day, week etc... Now if I have a program that does not recognize year 2000 it will search for the date (Year) for a period of time. If it does not find it then a loop is created and placed in the buffer. Now comes the problem. When the buffer is full the system can shutdown, be degraded or begin to act up. The concern is that it could take hours, days, even weeks before the buffer is full.
Simple Example: A fire alarm panel each day at midnight registers the date in this format- Month Day Year- Now on Dec 31, 1999 at midnight it does not recognize year 2000. So it attempts to complete the command "store date". When this fails over a period of time a loop is created in the buffer. This continues for two weeks. At the end of two weeks the buffer is full. No place to send the command so the system shutdown, becomes degraded, or begins to send out erroneous commands.
Concerns Shutdown the system and restarting could clear the buffer and then the process restarts again. Degraded systems could fail when need the most. Programs that are running and erroneous commands are sent out. I.E....... open value to 30 percent rather than 10 percent at the temperature of 70 degrees. Hope this helps explains things that can go bump in the night.
Now the 7 day clock example. The system is set to run for a 24 hour period for 7 days and restart. During the first 5 days it does certain commands, then on the 6 and 7 days the command change. Normal operation. Now lets change from its 5 and 2 schedule and modify it with a holiday. For the first four days the system runs fine. On the fifth day it cannot recognize the change in pattern. It loops into the buffer and can again fail, become degraded etc.... Since not all holidays fall under on the same day of the week this could become a problem through-out the year when the holidays move around on different days of the week. Traffic lights are a prime example of this possibly. Since January 1, 2000 fell on a Saturday the system did not have a problem with 5x2. Now Martin Luther King day is the first holiday of the New Year. The system works over the weekend and is ready for the new week to start. Monday is not part of its normal schedule.(FIRST OF FIVE) It attempts to run the new programmed date but can not. Older systems that have worked for a long time may have been programmed prior to Martin Luther King day becoming an offical holiday.
This could become very interesting.
Could explain alot, huh?
-- Electman (firstname.lastname@example.org), January 18, 2000
Well Newcomer, Where has your handle and information been for the past eight months?
-- Smell a (email@example.com), January 18, 2000.
Hello there Electman
Welcome to the frey sir. May I add a little something to your post? There are times, while installing an embedded system out in the feild. That there is suddenly a need found for a "date" counter in an operation. All it takes is a soldering pencil,date counter chips and a purposefull need to modify said controlls. This informal method is used quite frequently, in of all projects...A refinery.
Many people do not know that there are no recently built refineries in the United States. Only old ones; which have been up dated with digital control systems. (so as to need fewer personel to run the plant).(Gotta save on the bottom line you know). Now we face a year of uncertainty.
-- Shakey (firstname.lastname@example.org), January 18, 2000.
Some good points here.
-- Dee (T1Colt556@aol.com), January 18, 2000.
Hmmmm. Could your e-mail be a printout or re-format of something which origially appeared on this board about 2 weeks ago? Sounds rather familiar ...... Good to know we're here at the source of much good info.
-- Squirel Hunter (nuts@needa .newaddress), January 18, 2000.
As mentioned, it was an email, and it very well could of been posted here a few weeks ago... seeing how I was not the only one who recieved the email, and also seeing how I am new to this forum.
Thanks much for the warm welcome.
-- Electman (email@example.com), January 18, 2000.