| 摘要 |
PURPOSE:To prevent malfunction of an alarm signal due to spike noise by adding a polling circuit polling an alarm signal for an optional number of times so as to always monitor the alarm signal. CONSTITUTION:A polling circuit 5 uses a clock frequency-divided optionally by a frequency divider circuit 4 to decide the polling interval thereby monitoring an alarm signal outputted from an alarm signal generating circuit 3. At first an output signal of the alarm signal generating circuit 3 is given to the polling circuit 5 and a clock signal frequency-divided optionally by the frequency divider circuit 4 is given to the polling circuit 5. Then the number of times of polling is decided by a shift register comprising D flip-flop of an optional number in the polling circuit 5 and other D flip-flop of the same number as the polling number of times always monitor the alarm signal and it is judged to be normal only when the output data of the D flip-flop are coincident so as to prevent malfunction of the alarm signal. |
