Abstract: The timer circuit according to this invention has a first circuit block to which a source voltage is applied at all times and which includes a memory circuit which is set when an input signal is applied thereto. The timer circuit also has a reference voltage circuit which outputs a reference voltage when the memory circuit is set and which ceases to output the reference voltage when the memory circuit is reset, an oscillation circuit which outputs a train of pulse signals in a predetermined cycle, and a counter which begins to count the train of pulse signals after the reference voltage is outputted. The timer circuit further includes a second circuit block which includes a signal processing circuit which outputs a timer signal while the counter is counting. A reference voltage is supplied from the reference voltage circuit to the components of the second circuit block while the memory circuit remains set and the memory circuit is reset in response to a time-out signal from the counter.