Chapter 6 Clock Generator; Functions Of Clock Generator; Configuration Of Clock Generator - NEC 78K0 User Manual

6.1

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
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
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
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 : X1 input clock oscillation frequency
XP
2. f : Ring-OSC clock oscillation frequency
R
3. f : Subsystem clock oscillation frequency
XT
6.2

Configuration of Clock Generator

The clock generator consists of the following hardware.
Item
Control registers
Oscillator

CHAPTER 6 CLOCK GENERATOR

= 2.0 to 10.0 MHz. Oscillation can be stopped by executing the STOP
XP
= 240 kHz (TYP.). Oscillation can be stopped by setting the
R
*
Table 6-1. Configuration of Clock Generator
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
User's Manual U15947EJ2V0UD
= 32.768 kHz. Oscillation cannot be stopped. When
XT
Configuration
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