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Real Time Clock ICs — Parallax Forums

Real Time Clock ICs

piguy101piguy101 Posts: 248
edited 2011-07-29 05:26 in General Discussion
Would this IC work with the BS2?

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=NJU6355ED-ND

If so, how? I don't understand the data sheet at all with the bad English on it.
If not, is there another Real Time Cock IC (from DIgikey) that would work with the BS2?

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2011-07-27 17:20
    The Dallas/Maxim DS1302 works fine with the BS2. There's a pair of Nuts and Volts Columns that explains how (Volume 1, #33 and #34). Use the Resources tab on the main Parallax webpage for a link to the Nuts and Volts Columns index.
  • piguy101piguy101 Posts: 248
    edited 2011-07-27 17:23
    Thank you.
  • Tracy AllenTracy Allen Posts: 6,666
    edited 2011-07-28 15:17
    If you have the NJU6355, there is a great description of how to use it with the BS2 in Scott Edward's original documentation for the DCPB (data collection protoboard). There, he uses a 0.05F capacitor to back up timekeeping for several hours. Like the DS1302, it uses the native SHIFT commands on the BS2, and it can operate from 2V to 5.5V.
  • piguy101piguy101 Posts: 248
    edited 2011-07-28 17:39
    Dang, there are too many choices for RTCs, how do I know which one is best? Also, how do I know what crystal I need for the RTC, all the data sheet specifies is 32.768kHz?

    EDIT: YAY: Hundredth post!
  • TonyDTonyD Posts: 210
    edited 2011-07-29 00:45
    piguy101 wrote: »
    how do I know what crystal I need for the RTC, all the data sheet specifies is 32.768kHz?

    Yes, most RTC use a 32.768KHz crystal. At this frequency, when the RTC is operating from battery power, the power drain from the battery is small giving you better "standby" times.

    You can get RTC with different operating frequencies, the MC146818 used in the original IBM PC could operate from 1.048,576MHz and 4.194,304MHz.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2011-07-29 05:26
    piguy101 wrote: »
    Dang, there are too many choices for RTCs, how do I know which one is best? Also, how do I know what crystal I need for the RTC, all the data sheet specifies is 32.768kHz?

    You should also consider the DS3231 chip used in the ChronoDot from Adafruit or MaceTech

    It is compatible with the DS1307 and
    The DS3231 has an internal crystal and a switched bank of tuning capacitors. The temperature of the crystal is continously monitored, and the capacitors are adjusted to maintain a stable frequency. Other RTC solutions may drift minutes per month, especially in extreme temperature ranges...the ChronoDot will drift less than a minute per year. This makes the ChronoDot very well suited for time critical applications that cannot be regularly synchronized to an external clock.
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