PIC876 datasheet(123/218 Pages) MICROCHIP

123 / 218 page

 2001 Microchip Technology Inc.

DS30292C-page 121

PIC16F87X

12.2

Oscillator Configurations

12.2.1

OSCILLATOR TYPES

The PIC16F87X 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

PIC16F87X oscillator design requires the use of a par-

allel cut crystal. Use of a series cut crystal may give a

frequency out of the crystal manufacturers specifica-

tions. When in XT, LP or HS modes, the device can

have an external clock source to drive the OSC1/

CLKIN pin (Figure 12-2).

FIGURE 12-1:

CRYSTAL/CERAMIC

RESONATOR OPERATION

(HS, XT OR LP

OSC CONFIGURATION)

FIGURE 12-2:

EXTERNAL CLOCK INPUT

OPERATION (HS, XT OR

LP OSC

CONFIGURATION)

TABLE 12-1:

CERAMIC RESONATORS

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

PIC16F87X

(2)

Internal

Ranges Tested:

Mode

Freq.

OSC1

OSC2

455 kHz

2.0 MHz

4.0 MHz

68 - 100 pF

15 - 68 pF

68 - 100 pF

15 - 68 pF

8.0 MHz

16.0 MHz

10 - 68 pF

10 - 22 pF

10 - 68 pF

10 - 22 pF

These values are for design guidance only.

See notes following Table 12-2.

Resonators Used:

455 kHz

Panasonic EFO-A455K04B

± 0.3%

2.0 MHz

Murata Erie CSA2.00MG

± 0.5%

4.0 MHz

Murata Erie CSA4.00MG

± 0.5%

8.0 MHz

Murata Erie CSA8.00MT

± 0.5%

16.0 MHz

Murata Erie CSA16.00MX

± 0.5%

All resonators used did not have built-in capacitors.

OSC1

OSC2

Open

Clock from

Ext. System

PIC16F87X

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