Real-time clock Totally Explained

Everything about Real Time Clock totally explained

A real-time clock (RTC) is a computer clock (most often in the form of an integrated circuit) that keeps track of the current time. Although the term often refers to the devices in personal computers, servers and embedded systems, RTCs are present in almost any electronic device which needs to keep accurate time.

Terminology

The term is used to avoid confusion with ordinary hardware clocks which are only frequency standards that govern digital electronics, and don't count time in human units. RTC shouldn't be confused with real-time computing, which shares its three-letter acronym, but doesn't directly relate to time of day.

Purpose

Although keeping time can be done without an RTC, using one has benefits:

Low power consumption (important when running from alternate power)
Frees the main system for time-critical tasks
Sometimes more accurate than other methods (although personal computer RTC's are often inaccurate)

A GPS receiver can shorten its startup time by comparing the current time, according to its RTC, with the time at which it last had a valid signal. If it has been less than a few hours then the previous ephemeris is still usable.

Power source

RTCs often have an alternate source of power, so they can continue to keep time while the primary source of power is off or unavailable. This alternate source of power is normally a lithium battery in older systems, but some newer systems use a supercapacitor, because they're rechargeable and can be soldered. The alternate power source can also supply power to battery backed RAM.

Timing

Most RTCs use a crystal oscillator, but some use the power line frequency . In many cases the oscillator's frequency is 32.768 kHz.
Some microcontrollers have a real-time clock built in, generally only the ones with many other features and peripherals.

Further Information

Get more info on 'Real Time Clock'.

External Link Exchanges

Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:

<a href="http://real-time_clock.totallyexplained.com">Real-time clock Totally Explained</a>

Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned.