PIC16F74-ESLASHML datasheet(93/174 Pages) MICROCHIP

93 / 174 page

 2002 Microchip Technology Inc.

DS30325B-page 91

PIC16F7X

12.2

Oscillator Configurations

12.2.1

OSCILLATOR TYPES

The PIC16F7X can be operated in four different oscil-

lator modes. The user can program two configuration

bits (FOSC1 and FOSC0) to select one of these four

modes:

• LP

Low Power Crystal

• XT

Crystal/Resonator

• HS

High Speed Crystal/Resonator

• RC

Resistor/Capacitor

12.2.2

CRYSTAL OSCILLATOR/CERAMIC

RESONATORS

In XT, LP or HS modes, a crystal or ceramic resonator is

connected to the OSC1/CLKIN and OSC2/CLKOUT

pins

establish

oscillation

(Figure 12-1).

The

PIC16F7X oscillator design requires the use of a parallel

cut crystal. Use of a series cut crystal may give a fre-

quency out of the crystal manufacturers specifications.

When in HS mode, the device can accept an external

clock source to drive the OSC1/CLKIN pin (Figure 12-2).

See Figure 15-1 or Figure 15-2 (depending on the part

number and VDD range) for valid external clock

frequencies.

FIGURE 12-1:

CRYSTAL/CERAMIC

RESONATOR OPERATION

(HS, XT OR LP

OSC CONFIGURATION)

FIGURE 12-2:

EXTERNAL CLOCK INPUT

OPERATION (HS OSC

CONFIGURATION)

TABLE 12-1:

CERAMIC RESONATORS

(FOR DESIGN GUIDANCE

ONLY)

Note 1:

See Table 12-1 and Table 12-2 for recom-

mended values of C1 and C2.

2: A series resistor (RS) may be required for AT

strip cut crystals.

3: RF varies with the crystal chosen.

C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

SLEEP

Logic

PIC16F7X

RS(2)

Internal

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 were 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 at the bottom of page 92 for additional

information.

Resonators Used:

455 kHz

Panasonic EFO-A455K04B

2.0 MHz

Murata Erie CSA2.00MG

4.0 MHz

Murata Erie CSA4.00MG

8.0 MHz

Murata Erie CSA8.00MT

16.0 MHz

Murata Erie CSA16.00MX

OSC1

OSC2

Open

Clock from

Ext. System

PIC16F7X

(HS Mode)

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