12F615 datasheet(30/168 Pages) MICROCHIP

30 / 168 page

PIC12F609/615/12HV609/615

DS41302A-page 28

Preliminary

3.3.4

EXTERNAL RC MODES

The external Resistor-Capacitor (RC) modes support

the use of an external RC circuit. This allows the

designer maximum flexibility in frequency choice while

keeping costs to a minimum when clock accuracy is not

required. There are two modes: RC and RCIO.

In RC mode, the RC circuit connects to OSC1.

OSC2/CLKOUT outputs the RC oscillator frequency

divided by 4. This signal may be used to provide a clock

for external circuitry, synchronization, calibration, test

or other application requirements. Figure 3-5 shows

the external RC mode connections.

FIGURE 3-5:

EXTERNAL RC MODES

In RCIO mode, the RC circuit is connected to OSC1.

OSC2 becomes an additional general purpose I/O pin.

The RC oscillator frequency is a function of the supply

voltage, the resistor (REXT) and capacitor (CEXT) values

and the operating temperature. Other factors affecting

the oscillator frequency are:

• threshold voltage variation

• component tolerances

• packaging variations in capacitance

The user also needs to take into account variation due

to tolerance of external RC components used.

3.4

Internal Clock Modes

The Oscillator module provides a selectable system

clock source of either 4 MHz or 8 MHz. The selectable

frequency is configured through the IOSCFS bit of the

Configuration Word.

The frequency of the internal oscillator can be trimmed

with a calibration value in the OSCTUNE register.

3.4.1

INTOSC AND INTOSCIO MODES

The INTOSC and INTOSCIO modes configure the

internal oscillators as the system clock source when

the device is programmed using the oscillator selection

or the FOSC<2:0> bits in the Configuration Word

(CONFIG).

See

Section 11.0

“Special

Features of the CPU” for more information.

In INTOSC mode, OSC1/CLKIN is available for general

purpose I/O. OSC2/CLKOUT outputs the selected

internal oscillator frequency divided by 4. The CLKOUT

signal may be used to provide a clock for external

circuitry, synchronization, calibration, test or other

application requirements.

In INTOSCIO mode, OSC1/CLKIN and OSC2/CLKOUT

are available for general purpose I/O.

OSC2/CLKOUT(1)

CEXT

REXT

PIC® MCU

OSC1/CLKIN

FOSC/4 or

Internal

Clock

VDD

VSS

Recommended values: 10 k

Ω ≤ REXT ≤ 100 kΩ, <3V

3 k

Ω ≤ REXT ≤ 100 kΩ, 3-5V

CEXT > 20 pF, 2-5V

Note

Alternate pin functions are listed in

Section 1.0 “Device Overview”.

Output depends upon RC or RCIO Clock

mode.

I/O(2)

12F615 Datasheet(PDF) 30 Page - Microchip Technology

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