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Method of determining the condition of a back-up battery for a real time clock

  • US 5,596,512 A
  • Filed: 04/17/1996
  • Issued: 01/21/1997
  • Est. Priority Date: 08/15/1994
  • Status: Expired due to Fees
First Claim
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1. A method of determining the condition of a battery which backs up a real-time clock (RTC) when a main power supply for the RTC fails or is disconnected, comprising the steps of:

  • storing a time value of the RTC in non-volatile memory means while powered by the main power supply, just prior to a loss of the main power supply,detecting return of the main power supply,comparing the time value of the RTC upon return of the main power supply with said stored time value of the RTC,and indicating that the back-up battery is bad when the comparison step finds a predetermined relationship between the compared time values.

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