| 摘要 |
PURPOSE:To detect the runaway state of a microcomputer in simple configuration. CONSTITUTION:An integration circuit 62 converts a watch dog pulse led to a line 61 by a microcomputer 51 into voltage V corresponding to its duty ratio. The level of the voltage V is discriminated by reference voltage V1. V2 in comparators 71, 72. When the microcomputer 51 is brought into the runaway state, the duty ratio of the watch dog pulse takes a value different from that in normal operation time. Accordingly, the output voltage V of the integration circuit 62 may exceed the reference voltage V1 or drop below the reference voltage V2. At this time, a low level signal is led to a line 66. The low level signal is given to a reset input terminal RESET of the microcomputer 51 as a runaway state detection signal. |
