| 摘要 |
PURPOSE:To correct a time of a hardware clock accurately in a subsystem even when inter-system communication is in congestion by sending a time notice request, receiving time notice information of a main system and adding a calculated delay time to correct the time of the hardware clock. CONSTITUTION:A delay time calculation means 5 of a subsystem 3 measures a time from a transmission time t1 of a time notice request to a reception time t3 of time notice information based on the time of a hardware clock 4, uses a delay coefficient as (k), measures a time t2 of the clock of a hardware clock 2 of a main system 1, that is, t2=t3-(t3-t1)/k and obtains a delay time (a) as (t3-t2). Then a time correction means 6 adds the calculated delay time (a) to a time of time notice information from the main system 1 as a current time to correct the time of the hardware clock 4. Thus, even when the inter- system communication is in congestion, the time of the hardware clock 4 in the subsystem 3 is accurately corrected.
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