Subsystem Clock Oscillator - NEC mPD780344 Series User Manual

5.4.2 Subsystem clock oscillator

The subsystem clock oscillator oscillates with a crystal resonator (32.768 kHz TYP.) connected to the XT1 and
XT2 pins.
External clocks can be input to the subsystem clock oscillator. In this case, input a clock signal to the XT1 pin
and an inverted-phase clock signal to the XT2 pin.
Figure 5-6 shows an external circuit of the subsystem clock oscillator.
Figure 5-6. External Circuit of Subsystem Clock Oscillator
(a) Crystal oscillation
V
SS1
Caution When using the main system clock oscillator and subsystem clock oscillator, wire as follows in
the area enclosed by the broken lines in the 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 and do not route the wiring near a signal
line through which a high fluctuating current flows.
• Always make the ground point of the oscillator capacitor the same potential as V
ground the capacitor to a ground pattern through which a high current flows.
• Do not fetch signals from the oscillator.
Note that the subsystem clock oscillator is designed as a low-amplitude circuit for reducing
power consumption.
CHAPTER 5 CLOCK GENERATOR
IC
XT1
32.768
kHz
XT2
User's Manual U15798EJ2V0UD
(b) External clock
External
XT1
clock
XT2
. Do not
SS1
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