UPD78F9418A NEC, UPD78F9418A Datasheet - Page 95

• Manufacturer Part Number: UPD78F9418A
• Description: (UPD7894xxA) 8-Bit Single Chip Microcontrollers
• Manufacturer: NEC

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5.4.2 Subsystem clock oscillator
and XT2 pins.
inverted signal to the XT2 pin.
Caution
The subsystem clock oscillator is oscillated by a crystal resonator (32.768 kHz TYP.) connected across the XT1
An external clock can also be input to the circuit. In this case, input the clock signal to the XT1 pin, and input the
Figure 5-6 shows the external circuit of the subsystem clock oscillator.
When using the main system or subsystem clock oscillator, wire as follows in the area enclosed
by the broken lines in Figures 5-5 and 5-6 to avoid an adverse effect from wiring capacitance.
• • • • Keep the wiring length as short as possible.
• • • • Do not cross the wiring with the other signal lines. Do not route the wiring near a signal line
• • • • Always make the ground point of the oscillator capacitor the same potential as V
• • • • Do not fetch signals from the oscillator.
When using the subsystem clock oscillator, pay special attention because the subsystem clock
oscillator has low amplification to minimize current consumption.
through which a high fluctuating current flows.
Do not ground the capacitor to a ground pattern through which a high current flows.
(a) Crystal oscillation
Crystal resonator
Figure 5-6. External Circuit of Subsystem Clock Oscillator
32.768
kHz
V
XT1
XT2
SS0
, V
CHAPTER 5 CLOCK GENERATOR
SS1
User’s Manual U13952EJ3V0UD
External
clock
(b) External clock
XT1
XT2
SS0
and V
SS1
95
.