RL78/G10 CHAPTER 5 CLOCK GENERATOR
R01UH0384EJ0311 Rev. 3.11 75
Dec 22, 2016
CHAPTER 5 CLOCK GENERATOR
5.1 Functions of Clock Generator
The clock generator generates the clock to be supplied to the CPU and peripheral hardware.
The following three kinds of system clocks and clock oscillators are selectable.
(1) Main system clock
<1> X1 oscillator (16-pin products only)
This circuit oscillates a clock of f
X = 1 to 20 MHz by connecting a resonator to X1 and X2 pins.
The external main system clock (f
EX = 1 to 20 MHz) can also be supplied from EXCLK/X2/P122 pin.
Oscillation can be stopped or the external main system clock input can be disabled by executing the STOP
instruction or setting of the MSTOP bit (bit 7 of the clock operation status control register (CSC)).
<2> High-speed on-chip oscillator
The frequency at which to oscillate can be selected from among f
IH = 20/10/5/2.5/1.25 MHz (typ.) by using the
option byte (000C2H). After a reset release, the CPU always starts operating with this high-speed on-chip
oscillator clock. Oscillation can be stopped by executing the STOP instruction or setting the HIOSTOP bit (bit
0 of the CSC register).
The frequency specified by using an option byte can be changed by using the high-speed on-chip oscillator
frequency select register (HOCODIV). For details about the frequency, see Figure 5-9 Format of High-
Speed On-Chip Oscillator Frequency Selection Register (HOCODIV).
The frequencies that can be specified for the high-speed on-chip oscillator by using the option byte and the
high-speed on-chip oscillator frequency select register (HOCODIV) are shown below.
Power Supply Voltage Oscillation Frequency (MHz)
1.25 2.5 5 10 20
2.7 V ≤ VDD ≤ 5.5 V
√ √ √ √ √
2.0 V ≤ VDD ≤ 5.5 V
Note
√ √ √ − −
Remark √: Can operate, -: Cannot operate
As the main system clock, a high-speed system clock (X1 clock) or high-speed on-chip oscillator clock can be
selected by setting of the MCM0 bit (bit 4 of the system clock control register (CKC)).
Note Use this product within the voltage range from 2.25 to 5.5 V because the detection voltage (V
SPOR) of the
selectable power-on-reset (SPOR) circuit should also be considered.
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