| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To eliminate such a failure that it is necessary to change the multiplication factor of a PLL circuit according to a clock signal to be inputted in a microcontroller where a PLL circuit is mounted, it is necessary to change the multiplication factor by using an exclusive terminal or software by a CPU. <P>SOLUTION: This microcontroller is provided with a counter circuit 13 of a clock signal CK, an internal oscillation circuit 11 for outputting an internal oscillation signal S1, a counter control circuit 12 for generating a counter control signal S2 for controlling the counter circuit 13 from the internal oscillation signal and the clock signal, a PLL control circuit 14 for generating a PLL control signal S3 from a count value K2 of the counter circuit and a PLL circuit 15 for generating a clock signal CK2 by multiplying the clock signal by a multiplication factor shown by the PLL control signal. The frequency of the clock signal is automatically discriminated, and the optimal multiplication factor is determined by using the determination result. As a result, it is possible to attain a PLL circuit control without requiring any processing in any exclusive terminal or exclusive software. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
