NEC MuPD78F0132H, Руководство пользователя

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User’s Manual U16899EJ2V0UD
109
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.
•
High-speed system clock oscillator
The high-speed system clock oscillator oscillates a clock of f
XP
= 2.0 to 16.0 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 the option byte and the high-
speed system 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
: High-speed system 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 High-speed system clock oscillator
Ring-OSC oscillator
Subsystem clock oscillator