| 摘要 |
PURPOSE:To surely detect the runaway of a CPU by resetting the CPU when the value of a program counter is not equal to a normal level at a time point when an interruption is generated. CONSTITUTION:A timer 2 generates pulses periodically and therefore a CPU 1 receives an interruption and outputs a write clock. The write clock is not outputted if the CPU 1 has the runaway. Thus a reset pulse is generated via an FF 3 and an FF and then applied to a reset terminal RST of the CPU 1 via an OR circuit 7 to reset the CPU 1. While the contents of a program counter set immediately before the interruption is generated are held by a stack register in the CPU 1. A ROM 5 checks whether the contents of the stack register have normal values or not and gives the contents to a terminal RST of the CPU 1 via the circuit 7 when said contents have no normal value to set the CPU 1.
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