| 摘要 |
PURPOSE:To identify and interrupt a fault at the fault of a specific hardware clock and to continue the collation processing with a remaining hardware clock by providing a software clock adopting timer interruption as a reference and duplicated hardware clocks on a time collation system and using the decision logic of a time difference between the three timers. CONSTITUTION:A software clock 2 is provided in a memory section in a central processing unit CPU 11 and hardware clocks 3, 4 incorporating a high accuracy oscillator are connected to a CPU 1. The software clock 2 and the hardware clocks 3, 4 are collated periodically by the CPU 1, which calculates time differences T 1, T 2, T 3, T 4. When the difference T 1 resulting from the collation between the hardware clock 3 and the software clock 2 is smaller than the difference T1 and the difference T 2 between the hardware clocks 3 and 4 is smaller than the difference T2, both the hardware clocks 3, 4 are regarded to be normal to correct the software clock 2 by a prescribed correction method. Moreover, when the difference T 2 is larger than the T2, either of the hardware clocks 3, 4 is decided to be faulty. |
