Browse Prior Art Database

Microprocessor Clock/Calendar Error Detection and Correction Scheme for Battery Powered Clocks

IP.com Disclosure Number: IPCOM000107231D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Boguski, MJ: AUTHOR [+3]

Abstract

Disclosed is a method of detecting and temporarily correcting failures in time and date circuitry in microprocessor-based systems that require a valid system time and date to be available for proper system operation. The solution is twofold, involving a specific hardware implementation along with detection and correction software. The advantage of temporarily correcting the time is that repair may be deferred while still maintaining correct time to the system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 90% of the total text.

Microprocessor Clock/Calendar Error Detection and Correction Scheme for Battery Powered Clocks

      Disclosed is a method of detecting and temporarily correcting
failures in time and date circuitry in microprocessor-based systems
that require a valid system time and date to be available for proper
system operation. The solution is twofold, involving a specific
hardware implementation along with detection and correction software.
The advantage of temporarily correcting the time is that repair may
be deferred while still maintaining correct time to the system.

      When maintenance of system time and date is required it is
standard practice that the date and time is maintained by a battery
while the system is powered off.  When this single battery fails, two
problems occur; the system clock runs slower, and the integrity of
the system time and date is compromised.

      The hardware implementation is to use two clock designs with
significantly different failure rates (easily accomplished using
different batteries with different lives).  One battery will fail
before the other and its clock will run slower.

      Next, during system initialization, software is used to read
both clocks and compare them.  When the clocks differ by a
predetermined amount, an error condition is stored. The software then
takes the more recent time, writes it to the slower clock (making its
time correct while the system remains powered on) and allows the
system to continue ope...