UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 197

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

(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)
<4> Waiting for the stabilization of the oscillation of X1 clock
Cautions 1. Do not change the value of EXCLK and OSCSEL while the X1 clock is operating.
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
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.
Check the OSTC register and wait for the necessary time.
During the wait time, other software processing can be executed with the internal high-speed oscillation
clock.
AMPH
EXCLK
2. Set the X1 clock after the supply voltage has reached the operable voltage of the clock to
0
1
0
AMPH can be changed only once after a reset release. When AMPH is set to 1, the
clock supply to the CPU is stopped for 4.06 to 16.12 s.
Note
be used (see CHAPTER 29 ELECTRICAL SPECIFICATIONS ((A) GRADE PRODUCTS)).
IN
: High-speed system clock oscillation frequency
4 MHz
10 MHz < f
OSCSEL
1
f
IN
IN
X1 oscillation mode
Operation Mode of High-
Speed System Clock Pin
10 MHz
20 MHz
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
Operating Frequency Control
Crystal/ceramic resonator connection
P121/X1 Pin
P122/X2/EXCLK Pin
195