Fujitsu F2MCTM-16LX Hardware Manual page 109

Machine clock
The machine clock controls the operation of the CPU and peripheral functions. One cycle of machine clock
is regarded as one machine cycle (1/φ). An operating machine clock can be selected from among the main
clock, sub-clock, and five types of PLL clock.
Note:
When the operating voltage is 5 V, the oscillation clock can be between 3 MHz and 16 MHz. When an
external clock source is used, its frequency can be between 3 MHz and 24 MHz. The highest operating
frequency for the CPU and peripheral resource is 24 MHz. However, normal operation is not
guaranteed if a multiplication ratio resulting in a higher frequency than 24 MHz is specified.
Therefore, when 24 MHz external clock is inputted, 1 can be specified for the PLL clock multiplication
ratio. The PLL oscillation operates at the range of 4 MHz to 24 MHz, but the PLL oscillation range
differs by operation voltage and multiplication ratio. See the data sheet for the details.
CHAPTER 5 CLOCKS
93