PIC16F1526 datasheet(56/354 Pages) MICROCHIP

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PIC16(L)F1526/27

DS41458A-page 56

Preliminary

 2011 Microchip Technology Inc.

5.2.2

INTERNAL CLOCK SOURCES

The device may be configured to use the internal oscil-

lator block as the system clock by performing one of the

following actions:

• Program the FOSC<2:0> bits in Configuration

Word 1 to select the INTOSC clock source, which

will be used as the default system clock upon a

device Reset.

• Write the SCS<1:0> bits in the OSCCON register

to switch the system clock source to the internal

oscillator during run-time. See Section 5.3

“Clock Switching”

for more information.

In INTOSC mode, OSC1/CLKIN is available for general

purpose I/O. OSC2/CLKOUT is available for general

purpose I/O or CLKOUT.

The function of the OSC2/CLKOUT pin is determined

by the state of the CLKOUTEN bit in Configuration

Word 1.

The internal oscillator block has two independent

oscillators that provides the internal system clock

source.

The

HFINTOSC

(High-Frequency

Internal

Oscillator) is factory calibrated and operates at

16 MHz.

The

LFINTOSC

(Low-Frequency

Internal

Oscillator) is uncalibrated and operates at

31 kHz.

5.2.2.1

HFINTOSC

The High-Frequency Internal Oscillator (HFINTOSC) is

a factory calibrated 16 MHz internal clock source.

The output of the HFINTOSC connects to a postscaler

and multiplexer (see Figure 5-1). The frequency derived

from the HFINTOSC can be selected via software using

the IRCF<3:0> bits of the OSCCON register. See

Section 5.2.2.4 “Internal Oscillator Clock Switch

Timing”

for more information.

The HFINTOSC is enabled by:

• Configure the IRCF<3:0> bits of the OSCCON

•FOSC<2:0> = 100, or

• Set the System Clock Source (SCS) bits of the

OSCCON register to ‘1x’.

The High-Frequency Internal Oscillator Ready bit

(HFIOFR) of the OSCSTAT register indicates when the

HFINTOSC is running and can be utilized.

The High-Frequency Internal Oscillator Status Stable

bit (HFIOFS) of the OSCSTAT register indicates when

the HFINTOSC is running within 0.5% of its final value.

5.2.2.2

LFINTOSC

The Low-Frequency Internal Oscillator (LFINTOSC) is

an uncalibrated 31 kHz internal clock source.

The output of the LFINTOSC connects to a postscaler

and multiplexer (see Figure 5-1). Select 31 kHz, via

software, using the IRCF<3:0> bits of the OSCCON

Clock Switch Timing”

for more information. The

LFINTOSC is also the frequency for the Power-up Timer

(PWRT), Watchdog Timer (WDT) and Fail-Safe Clock

Monitor (FSCM).

The LFINTOSC is enabled by selecting 31 kHz

(IRCF<3:0> bits of the OSCCON register = 000) as the

system clock source (SCS bits of the OSCCON

enabled:

• Configure the IRCF<3:0> bits of the OSCCON

•FOSC<2:0> = 100, or

• Set the System Clock Source (SCS) bits of the

OSCCON register to ‘1x’

Peripherals that use the LFINTOSC are:

• Power-up Timer (PWRT)

• Watchdog Timer (WDT)

• Fail-Safe Clock Monitor (FSCM)

The Low-Frequency Internal Oscillator Ready bit

(LFIOFR) of the OSCSTAT register indicates when the

LFINTOSC is running and can be utilized.

PIC16F1526 Datasheet(PDF) 56 Page - Microchip Technology

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