| 摘要 |
<p>PURPOSE: To automatically change a frequency without stopping the operation of a circuit by providing a logic circuit means which selectively gates a signal from either a first frequency generation means or a second frequency generation means on a microprocessor. CONSTITUTION: When the power of the circuit is up, the output of F/F 52 in random. When the Q output of F/F 52 and the input of a corresponding NOR gate 46 is 'high' (+5V), an oscillator X2 is disabled since the output of the NOR gate 46 is considered to be a 'low' level (0V). The Q' output of F/F 52 and the corresponding input of a NOR gate 48 and the 'low' levels. Thus, an oscillator X1 is enabled and a signal from the oscillator is supplied to XTAL1 of the microprocessor 30 through a NOR gate 50. When the output level of F/F 52 becomes inverse at the time of power up. the oscillator X2 is enabled and the oscillator X1 is disabled. Thus, the frequency can be changed without interrupting the circuit operation.</p> |
