
User’s Manual U16228EJ2V0UD
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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 system clock oscillators are available.
X1 oscillator
The X1 oscillator oscillates a clock of f
XP
= 2.0 to 10.0 MHz. Oscillation can be stopped by executing the STOP
instruction or setting the main OSC control register (MOC) and processor clock control register (PCC).
Ring-OSC oscillator
The Ring-OSC oscillator oscillates a clock of f
R
= 240 kHz (TYP.). Oscillation can be stopped by setting the
Ring-OSC mode register (RCM) when “Can be stopped by software” is set by a mask option and the X1 input
clock is used as the CPU clock.
Subsystem clock oscillator
The subsystem clock oscillator oscillates a clock of f
XT
= 32.768 kHz. Oscillation cannot be stopped. When
subsystem clock oscillator is not used, setting not to use the on-chip feedback resistor is possible using the
processor clock control register (PCC), and the operating current can be reduced in the STOP mode.
Remarks 1.
f
XP
: X1 input clock oscillation frequency
2.
f
R
: Ring-OSC clock oscillation frequency
3.
f
XT
: Subsystem clock oscillation frequency
5.2 Configuration of Clock Generator
The clock generator includes the following hardware.
Table 5-1. Configuration of Clock Generator
Item
Configuration
Control registers
Processor clock control register (PCC)
Ring-OSC mode register (RCM)
Main clock mode register (MCM)
Main OSC control register (MOC)
Oscillation stabilization time counter status register (OSTC)
Oscillation stabilization time select register (OSTS)
Oscillators
X1 oscillator
Ring-OSC oscillator
Subsystem clock oscillator