| 摘要 |
PURPOSE:To efficiently execute time calibration processing by determining a next time calibration processing time from an error between an internal clock and an external clock, the allowance value of the error in the internal clock to be set in an allowance value setting means and a present time calibration interval. CONSTITUTION:When the time calibration processing time, which is determined at the time of preceding time calibration processing, comes over, the error time of an internal clock 2 and an external clock 3 is detected by an error detecting means 10. On the other hand, the allowance value, which can be allowed, of the error in the internal clock can be registered from a system side into an allowance value setting means 20. From this allowance value, detected error time and present time calibration interval, the next time calibration processing time is determined by an arithmetic means 30 and the time of the external clock 3 is copied to the internal clock 2 by a copying means 40. Since the time interval up to the next time calibration processing time reflects the result of time calibration by such operation, the time calibration processing can be efficiently executed. |
