Patent ID: 6252826
Filing Date: 2001-06-26
Classification: G06F

Abstract:
A time control device for controlling stepping of internal time by referring to a reference time in an external time source comprising:a plurality of oscillators oscillating at a reference clock having the same frequency;a sampling unit for sampling the reference clocks oscillated by said oscillators according to a pulse supplied at every specified time interval by said external time source;a determining unit for calculating an amount of error by comparing the sampling values obtained by said sampling unit to an expected value equivalent to the specified time interval and determining whether oscillating precision of each of said oscillators is normal or not from the amount of error;a clock switching unit for switching the reference clock source to some other oscillator when said determining unit determines that the oscillating precision of the oscillator whose reference clock is currently being used is inferior; anda stepping control unit for controlling stepping of the internal time according to the reference clock of the oscillator to which said clock switching unit has switched the reference clock source.