| 摘要 |
<p>PURPOSE:To always detect run-away by providing a circuit so as to operate a counter only with a clock signal from one clock input terminal. CONSTITUTION:When a clock is inputted from either a low-speed clock input terminal 1 or a high-speed clock input terminal 2 and the level of the input terminal inputting no clock is fixed to 'Low' or 'High' level, the clock is supplied to a counter 8 by an exclusive OR circuit 5. Therefore, by fixing the low-speed clock input terminal 1 to the 'Low' or 'High' level in the case of using only the high-speed clock, the run-away is generated to execute the malfunction of a clock switching circuit 3, the counter 8 continues counting even when no system clock is supplied and after the lapse of fixed time, the reset signal of a microcomputer is outputted from a reset signal line 10. Thus, the microcomputer can be recovered from the run-away state.</p> |
