PIC16F676-ESLASHP datasheet(57/132 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS40039F-page 57

PIC16F630/676

9.2

Oscillator Configurations

9.2.1

OSCILLATOR TYPES

The PIC16F630/676 can be operated in eight different

Oscillator Option modes. The user can program three

Configuration bits (FOSC2 through FOSC0) to select

one of these eight modes:

• LP

Low-Power Crystal

• XT

Crystal/Resonator

• HS

High Speed Crystal/Resonator

• RC

External Resistor/Capacitor (2 modes)

• INTOSC Internal Oscillator (2 modes)

• EC

External Clock In

9.2.2

CRYSTAL OSCILLATOR / CERAMIC

RESONATORS

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

is connected to the OSC1 and OSC2 pins to establish

oscillation (see Figure 9-1). The PIC16F630/676 oscil-

lator design requires the use of a parallel cut crystal.

Use of a series cut crystal may yield a frequency

outside of the crystal manufacturers specifications.

When in XT, LP or HS modes, the device can have an

external clock source to drive the OSC1 pin (see

Figure 9-2).

FIGURE 9-1:

CRYSTAL OPERATION (OR

CERAMIC RESONATOR)

(HS, XT OR LP OSC

CONFIGURATION)

FIGURE 9-2:

EXTERNAL CLOCK INPUT

OPERATION (HS, XT, EC,

OR LP OSC

CONFIGURATION)

TABLE 9-1:

CAPACITOR SELECTION FOR

CERAMIC RESONATORS

TABLE 9-2:

CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

Note:

Additional information on oscillator config-

urations is available in the PIC® Mid-Range

Reference Manual, (DS33023).

Note

See Table 9-1 and Table 9-2 for recommended

values of C1 and C2.

A series resistor may be required for AT strip cut

crystals.

RF varies with the Oscillator mode selected

(Approx. value = 10 M



C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

Sleep

To Internal

PIC16F630/676

Logic

RS(2)

Ranges Characterized:

Mode

Freq

OSC1(C1)

OSC2(C2)

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

Note 1: Higher capacitance increases the stability

of the oscillator but also increases the

start-up time. These values are for design

guidance only. Since each resonator has

its own characteristics, the user should

consult the resonator manufacturer for

appropriate values of external

components.

Mode

Freq

OSC1(C1)

OSC2(C2)

32 kHz

68-100 pF

100 kHz

2 MHz

4 MHz

68-150 pF

15-30 pF

150-200 pF

15-30 pF

8 MHz

10 MHz

20 MHz

15-30 pF

Note 1: Higher capacitance increases the stability

of the oscillator but also increases the

start-up time. These values are for design

guidance only. Rs may be required in HS

mode as well as XT mode to avoid

overdriving crystals with low drive level

specification. Since each crystal has its

own characteristics, the user should

consult the crystal manufacturer for

appropriate values of external

components.

Clock from

External System

PIC16F630/676

OSC1

OSC2(1)

Open

Note 1: Functions as RA4 in EC Osc mode.

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