Fujitsu MB90390 Series Hardware Manual page 115

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Machine clock (φ)
The machine clock controls the operation of the CPU and peripheral functions. One clock cycle is regarded
as one machine cycle (1/φ). An operating machine clock can be selected from among the main clock
(whose frequency is the source clock frequency divided by 2) and the other six clocks (whose frequencies
are multiples of the source clock frequency).
Note:
Although an oscillation clock of 3 MHz to 8 MHz can be generated if the operating voltage is 5 V, the
maximum operating frequency for the CPU and peripheral functions is 24 MHz. If a frequency
multiplier rate or the peak frequency of the clock modulator exceeds the operating frequency as
specified, devices will not operate correctly.
■ Clock Supply Map
Since the machine clock generated in the clock generation block is supplied as the clock that controls the
operation of the CPU and peripheral functions, the operation of the CPU and the peripheral functions is
affected by switching between the main clock and the PLL clock (clock mode) and by a change in the PLL
clock multiplier. Since some peripheral functions receive frequency-divided output from the time-base
timer, a peripheral unit can select the clock best suited for this operation. Figure 5.1-1 shows the clock
supply map.
CHAPTER 5 CLOCKS
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