PIC16F1507-ESLASHSS. datasheet(45/278 Pages) MICROCHIP

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DS40001586D-page 45

PIC16(L)F1507

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<1:0> bits in Configuration

Words 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, CLKIN is available for general

purpose I/O. CLKOUT is available for general purpose

I/O or CLKOUT.

The function of the CLKOUT pin is determined by the

CLKOUTEN bit in Configuration Words.

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) 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 5.2.2.6 “Internal Oscillator Clock Switch

Timing”

for more information.

The HFINTOSC is enabled by:

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

•FOSC<1:0> = 00, or

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

OSCCON register to ‘1x’.

A fast start-up oscillator allows internal circuits to

power-up and stabilize before switching to HFINTOSC.

The High-Frequency Internal Oscillator Ready bit

(HFIOFR) of the OSCSTAT register indicates when the

HFINTOSC is running.

The High-Frequency Internal Oscillator 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

a 31 kHz internal clock source.

The output of the LFINTOSC connects to a multiplexer

(see Figure 5-1). Select 31 kHz, via software, using the

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

5.2.2.6 “Internal Oscillator Clock Switch Timing”

for

more information. The LFINTOSC is also the frequency

for the Power-up Timer (PWRT) and the, Watchdog

Timer (WDT).

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<1:0> = 00, 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)

The Low-Frequency Internal Oscillator Ready bit

(LFIOFR) of the OSCSTAT register indicates when the

LFINTOSC is running.

5.2.2.3

FRC

The FRC clock is an uncalibrated, nominal 600 kHz

peripheral clock source.

The FRC is automatically turned on by the peripherals

requesting the FRC clock.

The FRC clock continues to run during Sleep.

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