RL78/G10 CHAPTER 5 CLOCK GENERATOR
R01UH0384EJ0311 Rev. 3.11 91
Dec 22, 2016
5.4.2 High-speed on-chip oscillator
The high-speed on-chip oscillator is incorporated in the RL78/G10. The frequency can be selected from among 20, 10,
5, 2.5, or 1.25 MHz by using the option byte (000C2H). Oscillation can be controlled by bit 0 (HIOSTOP) of the clock
operation status control register (CSC)
Note
. The high-speed on-chip oscillator automatically starts oscillating after reset
release.
Note 16-pin products only.
5.4.3 Low-speed on-chip oscillator
The low-speed on-chip oscillator is incorporated in the RL78/G10.
The low-speed on-chip oscillator clock is used only as the watchdog timer and 12-bit interval timer
Note
clock. The low-
speed on-chip oscillator clock cannot be used as the CPU clock.
The low-speed on-chip oscillator runs while the watchdog timer is operating or when bit 4 (WUTMMCK0) in the
operation speed mode control register (OSMC)
Note
is set to 1.
The low-speed on-chip oscillator is stopped when the watchdog timer is stopped and WUTMMCK0 is set to 0.
Note 16-pin products only.
5.5 Clock Generator Operation
The clock generator generates the following clocks and controls the operation modes of the CPU, such as standby
mode (see Figure 5-1).
• Main system clock fMAIN
• High-speed system clock
Note
fMX
X1 clock
Note
fX
External main system clock
Note
fEX
• High-speed on-chip oscillator clock fIH
• Low-speed on-chip oscillator clock fIL
• CPU/peripheral hardware clock f
CLK
The CPU starts operation when the high-speed on-chip oscillator starts outputting after a reset release in the RL78/G10.
When the power supply voltage is turned on, the clock generator operation is shown in Figure 5-12.
Note 16-pin products only.
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