UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 199

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

(3) Example of setting procedure when using high-speed system clock as CPU clock and peripheral
hardware clock
<1> Setting high-speed system clock oscillation
<2> Setting the high-speed system clock as the main system clock (MCM register)
<3> Setting the main system clock as the CPU clock and selecting the division ratio (PCC register)
Note The setting of <1> is not necessary when high-speed system clock is already operating.
(See 5.6.1 (1) Example of setting procedure when oscillating the X1 clock and (2) Example of
setting procedure when using the external main system clock.)
When XSEL and MCM0 are set to 1, the high-speed system clock is supplied as the main system clock
and peripheral hardware clock.
Caution If the high-speed system clock is selected as the main system clock, a clock
When CSS is cleared to 0, the main system clock is supplied to the CPU. To select the CPU clock
division ratio, use PCC0, PCC1, and PCC2.
XSEL
CSS
1
0
other than the high-speed system clock cannot be set as the peripheral
hardware clock.
MCM0
PCC2
1
0
0
0
0
1
Other than above
High-speed system clock (f
Selection of Main System Clock and Clock Supplied to Peripheral Hardware
PCC1
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
0
0
1
1
0
Main System Clock (f
PCC0
0
1
0
1
0
Note
MAIN
IN
f
f
f
f
f
Setting prohibited
MAIN
MAIN
MAIN
MAIN
MAIN
)
)
/2 (default)
/2
/2
/2
2
3
4
CPU Clock (f
High-speed system clock (f
Peripheral Hardware Clock (f
CPU
) Selection
IN
)
PRS
)
197