Renesas RL78/G15 User Manual

RL78/G15 CHAPTER 5 CLOCK GENERATOR
R01UH0959EJ0110 Rev.1.10 Page 150 of 765
Mar 7, 2023
5.4.2 High-speed on-chip oscillator
The high-speed on-chip oscillator is incorporated. The frequency can be selected from among 16, 8, 4, 2, or 1 MHz by
using the option byte (000C2H). Oscillation can be controlled by bit 0 (HIOSTOP) of the clock operation status control
register (CSC).
The high-speed on-chip oscillator automatically starts oscillating after reset release.
5.4.3 Low-speed on-chip oscillator
The low-speed on-chip oscillator is incorporated.
The low-speed on-chip oscillator clock is used only as the watchdog timer and 12-bit interval timer 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) is set to 1.
The low-speed on-chip oscillator is stopped when the watchdog timer is stopped and WUTMMCK0 is set to 0.
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 (f
MAIN
)
—
High-speed system clock
Note 1
(f
MX
)
X1 clock
Note 1
(f
X
)
External main system clock
Note 1
(f
EX
)
—
High-speed on-chip oscillator clock (f
IH
)
●
Low-speed on-chip oscillator clock (f
IL
)
●
CPU/peripheral hardware clock (f
CLK
)
The CPU starts operation when the high-speed on-chip oscillator starts outputting after a reset release.
When the power supply voltage is turned on, the clock generator operation is shown in Figure 5-13.
Note 1. 16-pin and 20-pin products only.

Renesas RL78/G15 Specifications

General

Brand	Renesas
Model	RL78/G15
Category	Microcontrollers
Language	English