Fujitsu MB91260B Series Hardware Manual page 38

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Oscillation Input in Power-on Sequence
When turning the power on, be sure to maintain clock input until the device is released from the oscillation
stabilization wait state.
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Note on Operation in PLL Clock Mode
On this microcontroller, if in case the crystal oscillator breaks off or an external reference clock input stops
while the PLL clock mode is selected, a self-oscillator circuit contained in the PLL may continue its
operation at its self-running frequency. However, Fujitsu will not guarantee results of operation if such
failure occurs.
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Note on Using an External Clock
When an external clock is used, in principle, supply the X0 pin with a clock signal and the X1 pin with a
clock signal opposite in phase to the signal to the X0 pin simultaneously. To use the STOP mode
(oscillation stop mode) along with the external clock, in which the X1 pin is disabled with "H" output, you
should insert an external resistor of about 1kΩ to prevent a collision between outputs.
Given below is an example of using an external clock.
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C Pin
As the MB91260B series contains a regulator, be sure to connect a bus capacitor of about 0.1 µF for the
regulator to the C pin.
Figure 2.1-1 Example of Using an External Clock
X0
X1
Figure 2.1-2 C Pin
C
MB91260B series
Vss
GND
CHAPTER 2 HANDLING DEVICES
MB91260B series
0.1 µF
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