This post has been edited 1 times, last edit by "Amateur" (Aug 2nd 2013, 8:52am)
I assume, that it takes separate time-keeping circuitry (chips, etc.) powered by either line voltage or battery, to maintain clock and date settings during power failures. Why is this absent in so many controllers when it’s so essential to proper automatic program operation? Is it merely a cost-saving factor?
Yes, an RTC or Real Time Clock is needed to keep the time. An RTC circuit consists of a crystal to generate cycles which is then converts into time, and a memory chip to keeps track of the time. The memory cannot be non-volatile because non-volatile memory chips have limited number of write operations and the chip will be worn out soon if it is constantly written. This is why an RTC circuit typically has a battery and a volatile memory chip. The power to run an RTC isn't much. It can run on a 3.3v coin battery for years, but it too, eventually dies. Then you just replace the battery, tell it the current time and the battery will keep it running.Thank you. So that means, I assume, that it takes separate time-keeping circuitry (chips, etc.) powered by either line voltage or battery, to maintain clock and date settings during power failures. Why is this absent in so many controllers when it’s so essential to proper automatic program operation? Is it merely a cost-saving factor?