NEC 78014Y Series, User Manual

Page: 160 / 547

www.DataSheet4U.com
CHAPTER 7 CLOCK GENERATOR
160
7.4 System Clock Oscillator
7.4.1 Main system clock oscillator
The main system clock oscillator oscillates with a crystal resonator or a ceramic resonator (standard: 10.0 MHz)
connected to the X1 and X2 pins.
External clocks can be input to the main system clock oscillator. In this case, input a clock signal to the X1 pin
and its inverted signal to the X2 pin.
Figure 7-4 shows an external circuit of the main system clock oscillator.
Figure 7-4. External Circuit of Main System Clock Oscillator
(a) Crystal or ceramic oscillation (b) External clock
Caution The STOP mode cannot be set while an external clock is being input. This is because the X1 pin
is short-circuited to V
SS
in the STOP mode.
7.4.2 Subsystem clock oscillator
The subsystem clock oscillator oscillates with a crystal resonator (standard: 32.768 kHz) 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 its inverted signal to the XT2 pin.
Figure 7-5 shows an external circuit of the subsystem clock oscillator.
Figure 7-5. External Circuit of Subsystem Clock Oscillator
(a) Crystal oscillation (b) External clock
Cautions are shown on the next page.
IC
X1
X2
Crystal or
Ceramic resonator
External
clock
X1
X2
PD74HCU04
µ
32.768
kHz
IC
XT1
XT2
External
clock
XT2
XT1
PD74HCU04
µ