PIC16F1934-ESLASHML datasheet(117/418 Pages) MICROCHIP

117 / 418 page

Preliminary

DS41364A-page 115

PIC16F193X/LF193X

8.5.7

FREQUENCY SELECT BITS (IRCF)

The output of the 16 MHz HFINTOSC and 31 kHz

LFINTOSC connects to a postscaler and multiplexer

(see Figure 8-1). The Internal Oscillator Frequency

Select bits IRCF<2:0> of the OSCCON register select

the frequency output of the internal oscillators. One of

eight frequencies can be selected via software:

•16 MHz

•8 MHz

•4 MHz

•2 MHz

•1 MHz

• 500 kHz (Default after Reset)

• 250 kHz

• 125 kHz

• 31 kHz (LFINTOSC)

8.5.8

INTERNAL OSCILLATOR CLOCK

SWITCH TIMING

When switching between the HFINTOSC, MFINTOSC

and the LFINTOSC, the new oscillator may already be

shut down to save power (see Figure 8-6). If this is the

case, there is a delay after the IRCF<3:0> bits of the

OSCCON register are modified before the frequency

selection takes place. The OSCSTAT register will

reflect the current active status of the HFINTOSC,

MFINTOSC and LFINTOSC oscillators. The sequence

of a frequency selection is as follows:

IRCF<3:0> bits of the OSCCON register are

modified.

If the new clock is shut down, a clock start-up

delay is started.

Clock switch circuitry waits for a falling edge of

the current clock.

The current clock is held low and the clock

switch circuitry waits for a rising edge in the new

clock.

The new clock is now active.

The OSCSTAT register is updated as required.

Clock switch is complete.

See Figure 8-6 for more details.

If the internal oscillator speed is switched between two

clocks of the same source, there is no start-up delay

before the new frequency is selected. Clock switching

time delays are shown in Table 8-1.

Start-up delay specifications are located in the

oscillator

tables

Section 28.0

“Electrical

Specifications”.

Note:

Following any Reset, the IRCF<2:0> bits of

the OSCCON register are set to ‘110’ and

the frequency selection is set to 4 MHz.

The user can modify the IRCF bits to

select a different frequency.

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