PIC12C67X datasheet(54/129 Pages) MICROCHIP

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PIC12C67X

DS30561B-page 54

9.2

Oscillator Configurations

9.2.1

OSCILLATOR TYPES

The PIC12C67X can be operated in seven different

oscillator

modes.

The user can program three

configuration bits (FOSC<2:0>) to select one of these

seven modes:

• LP:

Low Power Crystal

• HS:

High Speed Crystal/Resonator

• XT:

Crystal/Resonator

• INTRC*:

Internal 4 MHz Oscillator

• EXTRC*: External Resistor/Capacitor

*Can be configured to support CLKOUT

9.2.2

CRYSTAL OSCILLATOR / CERAMIC

RESONATORS

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

is connected to the GP5/OSC1/CLKIN and GP4/OSC2

pins

establish

oscillation

(Figure 9-1).

The

PIC12C67X oscillator design requires the use of a

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

frequency

out

the

crystal

manufacturers

specifications. When in XT, HS or LP modes, the

device can have an external clock source drive the

GP5/OSC1/CLKIN pin (Figure 9-2).

FIGURE 9-1:

CRYSTAL OPERATION

(OR CERAMIC RESONATOR)

(XT, HS OR LP OSC

CONFIGURATION)

FIGURE 9-2:

EXTERNAL CLOCK INPUT

OPERATION (XT, HS OR LP

OSC CONFIGURATION)

Note 1:

See Capacitor Selection tables for

recommended values of C1 and C2.

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

strip cut crystals.

3: RF varies with the oscillator mode selected

(approx. value = 10 M

Ω).

C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

SLEEP

To internal

logic

RS(2)

PIC12C67X

Clock from

ext. system

OSC1

OSC2

PIC12C67X

Open

TABLE 9-1:

CAPACITOR SELECTION

FOR CERAMIC RESONATORS

- PIC12C67X

TABLE 9-2:

CAPACITOR SELECTION

FOR CRYSTAL OSCILLATOR

- PIC12C67X

Osc

Type

Resonator

Freq

Cap. Range

455 kHz

2.0 MHz

4.0 MHz

22-100 pF

15-68 pF

22-100 pF

15-68 pF

4.0 MHz

8.0 MHz

10.0 MHz

15-68 pF

10-68 pF

10-22 pF

15-68 pF

10-68 pF

10-22 pF

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.

Osc

Type

Resonator

Freq

Cap. Range

32 kHz(1)

100 kHz

200 kHz

15 pF

15-30 pF

15 pF

30-47 pF

15-82 pF

100 kHz

200 kHz

455 kHz

1 MHz

2 MHz

4 MHz

15-30 pF

15-47 pF

200-300 pF

100-200 pF

15-100 pF

15-30 pF

15-47 pF

4 MHz

8 MHz

10 MHz

15-30 pF

Note 1:

For VDD > 4.5V, C1 = C2

≈ 30 pF is

recommended.

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 specifi-

cation. Since each crystal has its own characteris-

tics, the user should consult the crystal manufacturer

for appropriate values of external components.

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