PIC12F683 datasheet(21/148 Pages) MICROCHIP

21 / 148 page

 2004 Microchip Technology Inc.

Preliminary

DS41211B-page 19

PIC12F683

3.0

CLOCK SOURCES

3.1

Overview

The PIC12F683 has a wide variety of clock sources and

selection features to allow it to be used in a wide range

of applications while maximizing performance and mini-

mizing power consumption. Figure 3-1 illustrates a block

diagram of the PIC12F683 clock sources.

Clock sources can be configured from external oscilla-

tors, quartz crystal resonators, ceramic resonators and

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

tem clock source can be configured from one of two

internal oscillators, with a choice of speeds selectable

via software. Additional clock features include:

• Selectable system clock source between external

or internal via software.

• Two-Speed Clock 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 to the

internal oscillator.

The PIC12F683 can be configured in one of eight clock

modes.

EC – External clock with I/O on GP4.

LP – Low gain crystal or Ceramic Resonator

Oscillator mode.

XT – Medium gain crystal or Ceramic Resonator

Oscillator mode.

HS – High gain crystal or Ceramic Resonator

mode.

RC – External Resistor-Capacitor (RC) with

FOSC/4 output on GP4

RCIO – External Resistor-Capacitor with I/O on

GP4.

INTRC – Internal oscillator with FOSC/4 output

on GP4 and I/O on GP5.

INTRCIO – Internal oscillator with I/O on GP4

and GP5.

Clock source modes are configured by the FOSC<2:0>

bits

the

Configuration

Word

(see

Section 12.0 “Special Features of the CPU”). The

internal clock can be generated by two oscillators. The

HFINTOSC is a high-frequency calibrated oscillator. The

LFINTOSC is a low-frequency uncalibrated oscillator.

FIGURE 3-1:

PIC12F683 CLOCK SOURCE BLOCK DIAGRAM

(CPU and Peripherals)

OSC1

OSC2

Sleep

External Oscillator

LP, XT, HS, RC, RCIO, EC

System Clock

8 MHz

4 MHz

2 MHz

1 MHz

500 kHz

125 kHz

250 kHz

IRCF<2:0>

111

110

101

100

011

010

001

000

31 kHz

Power-up Timer (PWRT)

FOSC<2:0>

(Configuration Word)

SCS

(OSCCON<0>)

Internal Oscillator

(OSCCON<6:4>)

Watchdog Timer (WDT)

Fail-Safe Clock Monitor (FSCM)

HFINTOSC

8 MHz

LFINTOSC

31 kHz

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