During a brainstorming session today, we came up with the idea of performing an intentional shutdown on our manufacturing facility to: (1) spare our systems from the moment of rollover (2) have our embedded systems disconnected from a power source to force a reset to default conditions (this might require an extended shutdown period).

Has this idea been considered by any other activity and if so, how long of an extended shutdown could be considered adequate to allow internal memory power sources in embedded system to drain and allow a reset. Some of our PLCs have documentation which suggest that over one month of memory retention is possible, so we may be disconnecting pc board battery back-ups there. But undocumented systems such as CNC machines, test equipment and other commercial devices have us wondering.

Any comments or ideas?

WW

-- Anonymous, February 01, 1999

Answers

Response to Intentional Shutdowns As A Maens Of Control?

There are some RTC chips that have a built-in (right in the chip) lithium battery source, and they're rated to last for ten years...

As to whether or not any of your hardware has one of these little beasts, well, that's a completely different question.

Also, many embedded systems (like a PC motherboard) have lithium batteries somewhere in the circuit specifically to allow the RTC to keep time and to keep other parameter information when the power goes out. Those could last years as well.

Jon

-- Anonymous, February 01, 1999

I was figuring we would have to go in and temporarily remove any removable batteries. I'm more concerned about if we remove our equipment from any power source, how long for those with memory back- ups powered by capacitors. Some PLC's I've dealt with are rated to last eleven days with the battery removed.

An intentional disconnect might work, but only if we can have a high level of confidence about how long to keep the breakers open.

WW

-- Anonymous, February 02, 1999