PIC18F2220 datasheet(21/388 Pages) MICROCHIP

21 / 388 page

 2003 Microchip Technology Inc.

DS39599C-page 19

PIC18F2220/2320/4220/4320

2.0

OSCILLATOR

CONFIGURATIONS

2.1

Oscillator Types

The PIC18F2X20 and PIC18F4X20 devices can be

operated in ten different oscillator modes. The user can

program the configuration bits, FOSC3:FOSC0, in

Configuration Register 1H to select one of these ten

modes:

Low-Power Crystal

Crystal/Resonator

High-Speed Crystal/Resonator

HSPLL

High-Speed Crystal/Resonator

with PLL enabled

External Resistor/Capacitor with

FOSC/4 output on RA6

RCIO

External Resistor/Capacitor with

I/O on RA6

INTIO1

Internal Oscillator with FOSC/4

output on RA6 and I/O on RA7

INTIO2

Internal Oscillator with I/O on RA6

and RA7

External Clock with FOSC/4 output

10. ECIO

External Clock with I/O on RA6

2.2

Crystal Oscillator/Ceramic

Resonators

In XT, LP, HS or HSPLL Oscillator modes, a crystal or

ceramic resonator is connected to the OSC1 and

OSC2 pins to establish oscillation. Figure 2-1 shows

the pin connections.

The oscillator design requires the use of a parallel cut

crystal.

FIGURE 2-1:

CRYSTAL/CERAMIC

RESONATOR OPERATION

(XT, LP, HS OR HSPLL

CONFIGURATION)

TABLE 2-1:

CAPACITOR SELECTION FOR

CERAMIC RESONATORS

Note:

Use of a series cut crystal may give a fre-

quency out of the crystal manufacturers

specifications.

Typical Capacitor Values Used:

Mode

Freq

OSC1

OSC2

455 kHz

2.0 MHz

4.0 MHz

56 pF

47 pF

33 pF

56 pF

47 pF

33 pF

8.0 MHz

16.0 MHz

27 pF

22 pF

27 pF

22 pF

Capacitor values are for design guidance only.

These capacitors were tested with the resonators

listed below for basic start-up and operation. These

values are not optimized.

Different capacitor values may be required to produce

acceptable oscillator operation. The user should test

the performance of the oscillator over the expected

VDD and temperature range for the application.

See the notes on page 20 for additional information.

Resonators Used:

455 kHz

4.0 MHz

2.0 MHz

8.0 MHz

16.0 MHz

Note

See Table 2-1 and Table 2-2 for initial values

of C1 and C2.

A series resistor (RS) may be required for AT

strip cut crystals.

RF varies with the oscillator mode chosen.

C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

Sleep

Logic

PIC18FXXXX

RS(2)

Internal

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