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Real Time ClockHow to use
If the accuracy of time is ±20ppm, then the monthly rate is 53.6 seconds. The calculation formula is as follows:
±20ｘ10-6 x 60sec.ｘ60min.ｘ24hrs.ｘ31days = ±53.6 sec./month
Supposed that the monthly rate should be within 1 minute, the accuracy of time must be equal or less than ±23.14ppm.