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78K0/Fx2-L
5.6.2 Example of controlling internal high-speed oscillation clock
The following describes examples of clock setting procedures for the following cases.
(1) When restarting oscillation of the internal high-speed oscillation clock
(2) When using internal high-speed oscillation clock as CPU clock, and internal high-speed oscillation clock or high-
speed system clock as peripheral hardware clock
(3) When stopping the internal high-speed oscillation clock
Remark See 5.4.5 PLL (phase locked loop) when using the PLL.
(1) Example of setting procedure when restarting oscillation of the internal high-speed oscillation clock
<1> Setting restart of oscillation of the internal high-speed oscillation clock (RCM register)
When RSTOP is cleared to 0, the internal high-speed oscillation clock starts operating.
<2> Waiting for the oscillation accuracy stabilization time of internal high-speed oscillation clock (RCM register)
Wait until RSTS is set to 1
Notes 1. After a reset release, the internal high-speed oscillator automatically starts oscillating and the internal
high-speed oscillation clock is selected as the CPU clock.
2. This wait time is not necessary if high accuracy is not necessary for the CPU clock and peripheral
hardware clock.
(2) Example of setting procedure when using internal high-speed oscillation clock as CPU clock, and internal
high-speed oscillation clock or high-speed system clock as peripheral hardware clock
<1> • Restarting oscillation of the internal high-speed oscillation clock
(Refer to 5.6.2 (1) Example of setting procedure when restarting oscillation of the internal high-
speed oscillation clock).
• Oscillating the high-speed system clock
(This setting is required when using the high-speed system clock as the peripheral hardware clock. Refer
to 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.)
Note The setting of <1> is not necessary when the internal high-speed oscillation clock or high-speed
system clock is already operating.
<2> Selecting the clock supplied as the main system clock and peripheral hardware clock (MCM register)
Set the main system clock and peripheral hardware clock using XSEL and MCM0.
XSEL
0
0
1
R01UH0068EJ0203 Rev.2.03
Jun 29, 2012
Note 2
.
MCM0
Selection of Main System Clock and Clock Supplied to Peripheral Hardware
Main System Clock (f
0
Internal high-speed oscillation clock
(f
)
IH
1
0
CHAPTER 5 CLOCK GENERATOR
Note
Note
)
Peripheral Hardware Clock (f
XP
Internal high-speed oscillation clock
(f
)
IH
High-speed system clock (f
Note 1
)
PRS
)
XH
150
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