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Notes on external clock
When an external clock is used, the oscillation stabilization wait time is required at power-on reset or at
cancellation of sub-clock mode or stop mode. As shown in Figure 2.1-1 , when an external clock is used,
connect only the X0 pin and leave the X1 pin open.
Figure 2.1-1 Sample Application of External Clock
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Caution on operation during 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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Power supply pins
When a device has two or more Vcc or Vss pins, the pins that should have equal potential are connected
within the device in order to prevent a latch-up or other malfunction. To reduce extraneous emission, to
prevent a malfunction of the strobe signal due to an increase in the group level, and to maintain the local
output current rating, connect all these power supply pins to an external power supply and ground them.
The current source should be connected to the Vcc and Vss pins of the device with minimum impedance. It
is recommended that a bypass capacitor of about 0.1 µF be connected near the terminals between Vcc and
Vss.
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Analog power-on sequence of A/D converter
The power to the A/D converter (AVcc, AVR) and analog inputs (AN0 to AN7) must be turned on after the
power to the digital circuits (Vcc) is turned on. When turning off the power, turn off the power to the
digital circuits (Vcc) after turning off the power to the A/D converter and analog inputs. When the power
is turned on or off, AVR should not exceed AVcc. Also, when a pin that is used for analog input is also
used as an input port, the input voltage should not exceed AVcc. (The power to the analog circuits and the
power to the digital circuits can be simultaneously turned on or off.)
CHAPTER 2 NOTES ON HANDLING DEVICES
X0
MB90460/465 series
X1
Open
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