![](http://datasheet.mmic.net.cn/Renesas-Electronics-America/UPD78F0394GC-8EA-A_datasheet_99854/UPD78F0394GC-8EA-A_144.png)
CHAPTER 6 CLOCK GENERATOR
User’s Manual U17473EJ2V0UD
142
6.6.2 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
(1) Example of setting procedure when restarting oscillation of the internal high-speed oscillation clock
Note 1
<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
Note 2.
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 clockNote
(See 6.6.2 (1) Example of setting procedure when restarting internal high-speed oscillation
clock).
Oscillating the high-speed system clockNote
(This setting is required when using the high-speed system clock as the peripheral hardware clock.
See 6.6.1 (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.
Selection of Main System Clock and Clock Supplied to Peripheral Hardware
XSEL
MCM0
Main System Clock (fXP)
Peripheral Hardware Clock (fPRS)
0
1
Internal high-speed oscillation clock
(fRH)
1
0
Internal high-speed oscillation clock
(fRH)
High-speed system clock (fXH)