Chapter 5 Clock Generator; Functions Of Clock Generator; Configuration Of Clock Generator - NEC 78K0/KB1+ Preliminary User's Manual

5.1 Functions of Clock Generator

The clock generator generates the clock to be supplied to the CPU and peripheral hardware.
The following two system clock oscillators are available.
• High-speed system clock oscillator
The following two high-speed system clock oscillators are available.
Crystal/ceramic oscillator: Oscillates a clock of f
•
• External RC oscillator:
High-speed system clock oscillation can be selected using the option byte. Refer to CHAPTER 20 OPTION
BYTE for details.
The high-speed system clock oscillator can be stopped by executing the STOP instruction or setting the main
OSC control register (MOC).
• 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 the option byte and the high-
speed system clock is used as the CPU clock.
Remarks 1. f : High-speed system clock oscillation frequency
XP
2. f : Ring-OSC clock oscillation frequency
R

5.2 Configuration of Clock Generator

The clock generator includes the following hardware.
Item
Control registers
Oscillator
82

CHAPTER 5 CLOCK GENERATOR

Oscillates a clock of f
= 240 kHz (TYP.). Oscillation can be stopped by setting the
R
Table 5-1. 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)
System wait control register (VSWC)
High-speed system clock oscillator
Ring-OSC oscillator
Preliminary User's Manual U16846EJ1V0UD
= 2 to 16 MHz
XP
= 3 to 4 MHz
XP
Configuration