upd78f0730 Renesas Electronics Corporation., upd78f0730 Datasheet - Page 99

• Manufacturer Part Number: upd78f0730
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

5.6 Controlling Clock
5.6.1 Controlling high-speed system clock
pins.
The following two types of high-speed system clocks are available.
• X1 clock:
• External main system clock: External clock is input to the EXCLK pin.
When the high-speed system clock is not used, the X1/P121 and X2/EXCLK/P122 pins can be used as I/O port
Caution The X1/P121 and X2/EXCLK/P122 pins are in the I/O port mode after a reset release.
The following describes examples of setting procedures for the following cases.
(1) When oscillating X1 clock
(2) When using external main system clock
(3) When using high-speed system clock as CPU clock and peripheral hardware clock
(4) When stopping high-speed system clock
(1) Example of setting procedure when oscillating the X1 clock
<1> Setting frequency (OSCCTL register)
<2> Setting P121/X1 and P122/X2/EXCLK pins and selecting X1 clock or external clock (OSCCTL register)
<3> Controlling oscillation of X1 clock (MOC register)
Using AMPH, set the gain of the on-chip oscillator according to the frequency to be used.
Note Set AMPH before setting the peripheral functions after a reset release. The value of AMPH can
Remark f
When EXCLK is cleared to 0 and OSCSEL is set to 1, the mode is switched from port mode to X1
oscillation mode.
If MSTOP is cleared to 0, the X1 oscillator starts oscillating.
AMPH
EXCLK
0
1
0
be changed only once after a reset release. When AMPH is set to 1, the clock supply to the CPU
is stopped for 5
Note
XH
f
10 MHz < f
: High-speed system clock oscillation frequency
OSCSEL
XH
≤ 10 MHz
1
Crystal/ceramic resonator is connected across the X1 pin.
XH
µ
X1 oscillation mode
s (MIN.).
Operation Mode of High-
Speed System Clock Pin
Preliminary User’s Manual U19014EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
Operating Frequency Control
Crystal/ceramic resonator connection
P121/X1 Pin
P122/X2/EXCLK Pin
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