Issue
How do our field controllers keep their own internal time? ( Clock , Real Time Clock , RTC , Frequency)
Product Line
Andover Continuum
Environment
Continuum Controllers
Cause
Not sure how the local time is kept on the controllers.
Resolution
Throughout the life of the Infinity and Continuum product line, the method of keeping the time on the controllers has changed.
The older controllers (9000,9200,9400 era) used the AC frequency as a pulse, or heartbeat, to keep time. This was calculated at a 60Hz cycle and if there was a dirty power cycle or a different frequency power supply (say 50Hz), the local time on the controller would drift out over time.
The newer controllers (anything with a Real Time Clock) use the Real Time Clock and its crystal to keep the time; this is in no way affected by the AC or DC power.
On any newer generation controller that has a battery backup (battery backed RAM), the battery also keeps the Real Time Clock functioning as well as the controller RAM in case of a power failure.
