| 摘要 |
<p>PURPOSE:To curtail the power consumption and to extend a battery life by generating plural clocks so that a main clock of a microprocessor can be selected from among these plural clocks by the user and as a software. CONSTITUTION:When a battery circuit is turned on, a power-on resetting circuit is operated and outputs of ports P0, P1 of a parallel input/output port 5 become both '0'. In this case, a control signal selecting circuit 4 selects an input signal '0' of an input terminal D0 and output it as a clock selecting signal 8 from an output terminal Q, a clock selecting circuit 2 selects a clock 9 and outputs it to a microprocessor 1, and the microprocessor 1 executes its initial operation. Thereafter, a control signal 11 becomes a high level and the control signal selecting circuit 4 outputs an input signal of an input terminal D1, namely a signal corresponding to a state of a manual switch 7, as the clock selecting signal 8. As a result, to the microprocessor 1, the clock 9 or 10 which has been selected by a user is outputted from the clock selecting circuit 2, as a main clock.</p> |
