PIC18F23K22-ESLASHML datasheet(27/496 Pages) MICROCHIP

27 / 496 page

 2010 Microchip Technology Inc.

Preliminary

DS41412C-page 27

PIC18(L)F2X/4XK22

2.0

OSCILLATOR MODULE (WITH

FAIL-SAFE CLOCK MONITOR)

2.1

Overview

The oscillator module has a wide variety of clock

sources and selection features that allow it to be used

in a wide range of applications while maximizing perfor-

mance and minimizing power consumption. Figure 2-1

illustrates a block diagram of the oscillator module.

Clock sources can be configured from external

oscillators, quartz crystal resonators, ceramic resonators

and Resistor-Capacitor (RC) circuits. In addition, the

system clock source can be configured from one of three

internal oscillators, with a choice of speeds selectable via

software. Additional clock features include:

• Selectable system clock source between external

or internal sources via software.

• Two-Speed Start-up mode, which minimizes

latency between external oscillator start-up and

code execution.

• Fail-Safe Clock Monitor (FSCM) designed to

detect a failure of the external clock source (LP,

XT, HS, EC or RC modes) and switch

automatically to the internal oscillator.

• Oscillator Start-up Timer (OST) ensures stability

of crystal oscillator sources.

The primary clock module can be configured to provide

one of six clock sources as the primary clock.

External Resistor/Capacitor

Low-Power Crystal

Crystal/Resonator

INTOSC

Internal Oscillator

High-Speed Crystal/Resonator

External Clock

The HS and EC oscillator circuits can be optimized for

power consumption and oscillator speed using settings

in FOSC<3:0>. Additional FOSC<3:0> selections

enable RA6 to be used as I/O or CLKO (FOSC/4) for

RC, EC and INTOSC Oscillator modes.

Primary Clock modes are selectable

by the

FOSC<3:0> bits of the CONFIG1H Configuration

by these Configuration and register bits:

PRICLKEN (CONFIG1H<5>)

PRISD (OSCCON2<2>)

PLLCFG (CONFIG1H<4>)

PLLEN (OSCTUNE<6>)

HFOFST (CONFIG3H<3>)

IRCF<2:0> (OSCCON<6:4>)

MFIOSEL (OSCCON2<4>)

INTSRC (OSCTUNE<7>)

The HFINTOSC, MFINTOSC and LFINTOSC are

factory calibrated high, medium and low-frequency

oscillators, respectively, which are used as the internal

clock sources.

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