PIC12F508ESLASHMS datasheet(44/110 Pages) MICROCHIP

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PIC12F508/509/16F505

DS41236E-page 44

7.2

Oscillator Configurations

7.2.1

OSCILLATOR TYPES

The PIC12F508/509/16F505 devices can be operated

in up to six different oscillator modes. The user can

program up to three Configuration bits (FOSC<1:0>

[PIC12F508/509], FOSC<2:0> [PIC16F505]). To select

one of these modes:

• LP:

Low-Power Crystal

• XT:

Crystal/Resonator

• HS:

High-Speed Crystal/Resonator

(PIC16F505 only)

• INTRC: Internal 4 MHz Oscillator

• EXTRC: External Resistor/Capacitor

• EC:

External High-Speed Clock Input

(PIC16F505 only)

7.2.2

CRYSTAL OSCILLATOR/CERAMIC

RESONATORS

In HS (PIC16F505), XT or LP modes, a crystal or

ceramic resonator is connected to the (GP5/RB5)/

OSC1/(CLKIN) and (GP4/RB4)/OSC2/(CLKOUT) pins

to establish oscillation (Figure 7-1). The PIC12F508/

509/16F505 oscillator designs require the use of a

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

frequency

out

the

crystal

manufacturers

specifications. When in HS (PIC16F505), XT or LP

modes, the device can have an external clock source

drive the (GP5/RB5)/OSC1/CLKIN pin (Figure 7-2).

When the part is used in this fashion, the output drive

levels on the OSC2 pin are very weak. This pin should

be left open and unloaded. Also, when using this mode,

the external clock should observe the frequency limits

for the clock mode chosen (HS, XT or LP).

FIGURE 7-1:

CRYSTAL OPERATION

(OR CERAMIC

RESONATOR)

(HS, XT OR LP OSC

CONFIGURATION)

FIGURE 7-2:

EXTERNAL CLOCK INPUT

OPERATION (HS, XT OR

LP OSC

CONFIGURATION)

TABLE 7-1:

CAPACITOR SELECTION FOR

CERAMIC RESONATORS –

PIC12F508/509/16F505(1)

Note 1: This device has been designed to per-

form to the parameters of its data sheet.

It has been tested to an electrical

specification designed to determine its

conformance with these parameters.

Due

process

differences

the

manufacture of this device, this device

may have different performance charac-

teristics than its earlier version. These

differences may cause this device to

perform differently in your application

than the earlier version of this device.

2: The user should verify that the device

oscillator

starts

and

performs

expected. Adjusting the loading capacitor

values and/or the Oscillator mode may

be required.

Osc

Type

Resonator

Freq.

Cap. Range

4.0 MHz

30 pF

HS(2)

16 MHz

10-47 pF

Note 1:

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.

PIC16F505 only.

Note

See Capacitor Selection tables for

recommended values of C1 and C2.

A series resistor (RS) may be required for AT

strip cut crystals.

RF approx. value = 10 M

Ω.

C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

Sleep

To internal

logic

RS(2)

PIC12F508/509

PIC16F505

Clock from

ext. system

OSC1

OSC2

PIC16F505

Open

PIC12F508/509

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