UPD78F0138 NEC, UPD78F0138 Datasheet - Page 117

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

5.1 Functions of Clock Generator
5.2 Configuration 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
• Ring-OSC oscillator
• Subsystem clock oscillator
Remarks 1. f
The clock generator includes the following hardware.
Control registers
Oscillators
The X1 oscillator oscillates a clock of f
instruction or setting the main OSC control register (MOC) and processor clock control register (PCC).
The Ring-OSC oscillator oscillates a clock of f
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.
The subsystem clock oscillator oscillates a clock of f
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.
2. f
3. f
Item
XP
R
XT
:
: X1 input clock oscillation frequency
: Subsystem clock oscillation frequency
Ring-OSC clock oscillation frequency
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)
X1 oscillator
Ring-OSC oscillator
Subsystem clock oscillator
Table 5-1. Configuration of Clock Generator
CHAPTER 5 CLOCK GENERATOR
XP
User’s Manual U16228EJ2V0UD
= 2.0 to 10.0 MHz. Oscillation can be stopped by executing the STOP
R
= 240 kHz (TYP.). Oscillation can be stopped by setting the
XT
= 32.768 kHz. Oscillation cannot be stopped. When
Configuration
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