| 摘要 |
PURPOSE:To easily detect a clock stop by providing a service processor which reads the contents of a scan-out means periodically and compares them with a value read at the last time to detect the stop of a clock. CONSTITUTION:A 4-bit counter 11 continues to count as long as a clock oscillator 10 is in operation, and an SVP 20 reads the contents of the 4-bit counter 11 in the SVP 20 periodically through the scan-out means 12 under the control of software or firmware asynchronously with the counting operation and compares them with the last value. While the clock oscillator 10 is in operation, both values do not coincide with each other in general, but if the output of the clock oscillator 10 coincides with the period of a read from the SVP 20, both values have possibility of coincidence and the read-in period of the counter 11 is prevented from synchronizing with the period of the clock oscillator 10. Consequently, the read value of the SVP 20 is different from the last value at every time unless the clock oscillator 10 stops, so that the stop of the oscillator 10 is easily detected. |
