| 摘要 |
<p>A conventional watchdog timer circuit is arranged to judge a microcomputer (1) to be normal as long as a pulse signal is being outputted from the microcomputer (1). Therefore, an abnormal condition cannot be detected when an operating frequency of the microcomputer lowers, for example. As a solution, the watchdog timer circuit (3) is provided with a function for detecting the frequency. If the frequency of the pulse signal (31) deviates from a predetermined frequency range, a reset signal (32) is outputted indicating that the microcomputer (1) is abnormal, even if the pulse signal (31) is being outputted. A solenoid-operated gate valve (SV) is thereby closed to stop the supply of gas to a gas burner (B). <IMAGE></p> |
