| 摘要 |
<p>PURPOSE: To save the electric power without using an input/output port by disabling a reset signal for a normal operation mode by using am oscillation signal from an oscillator and setting a microprocessor to a stand-by mode. CONSTITUTION: The microprocessor 202 has the normal mode and stand-by mode and the oscillator 209 is controlled by the microprocessor 202. Once the stand-by mode is called, the oscillator 209 stops and the output voltage of a rectifier 210 drops, so that a transistor(TR) 216 turns off. When a key pad is pressed, a low-level voltage is developed on a sense line 204 of a matrix keyboard 205 to lower the voltage level at the base terminal of the TR 220, which is turned ON. Then the voltage at the reset terminal 206 of the microprocessor 202 becomes high, and consequently resetting is done in the stand-by mode, so that the microprocessor 202 begins to execute software present in its memory.</p> |
