| 摘要 |
<p>PURPOSE:To execute a stand-by control by a comparatively simple circuit, by impressing a stand-by start requesting signal to a set terminal of a latching circuit and setting it temporarily to a stand-by state, and releasing it after a prescribed time. CONSTITUTION:When shifting to a stand-by state, a stand-by start requesting signal S2 is impressed to a set terminal of an FF 51. As a result, the FF 51 is set, its Q output becomes a low level, and an output part of an inverter 53, namely, a voltage VN1 of a node N1 is shifted to a lo level. In this shifting process, a threshold value Vth1 of an inverter 55 is higher than a threshold value Vth2 of an inverter 54, therefore, an output of the inverter 55 becomes a high level and a stand-by starting signal S55 is impressed to a stand-by signal generating circuit 56. The circuit 56 outputs a stand-by signal S5 and sets an MPU 2, a memory 3 and an input/output part 4 to a stand-by state. Thereafter, when the voltage VN1 drops and reaches the threshold value Vth2, the FF 51 is reset. When said voltage reaches the minimum value, and thereafter, reaches the threshold value Vth1, the stand-by state is released and shifted to an operation state.</p> |
