Microchip Technology AC244045 Data Sheet

© 2009 Microchip Technology Inc.

DS41341E-page 89

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 performance and
minimizing power consumption. Figure 7-1 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 can be configured to use an internal calibrated
high-frequency oscillator as clock source, with a choice
of selectable speeds via software. 

Clock source modes are configured by the FOSC bits
in Configuration Word 1 (CONFIG1). The oscillator
module can be configured for one of eight modes of
operation.

1.

RC – External Resistor-Capacitor (RC) with
F

OSC

/4 output on OSC2/CLKOUT.

2.

RCIO – External Resistor-Capacitor (RC) with
I/O on OSC2/CLKOUT.

3.

INTOSC – Internal oscillator with F

OSC

/4 output

on OSC2 and I/O on OSC1/CLKIN.

4.

INTOSCIO – Internal oscillator with I/O on
OSC1/CLKIN and OSC2/CLKOUT.

5.

EC – External clock with I/O on OSC2/CLKOUT.

6.

HS – High Gain Crystal or Ceramic Resonator
mode.

7.

XT – Medium Gain Crystal or Ceramic
Resonator Oscillator mode.

8.

LP – Low-Power Crystal mode.

(CPU and Peripherals)

OSC1

OSC2

Sleep

LP, XT, HS, RC, EC

System Clock

P

o

stscale

r

MU

X

MU

X

16 MHz/500 kHz

8 MHz/250 kHz

4 MHz/125 kHz

2 MHz/62.5 kHz

IRCF<1:0>

11

10

01

00

FOSC<2:0>

(Configuration Word 1)

(OSCCON Register)

500 kHz

INTOSC

32x

MU

X

0

1

PLL

PLLEN

(Configuration Word 1)