PIC16LF1454 Datasheet, PDF (63/418 Pages) Microchip Technology – 14/20-Pin Flash, 8-Bit USB Microcontrollers with XLP Technology

5.2.2.2
Internal Oscillator Frequency
Adjustment
The 16 MHz internal oscillator is factory calibrated.
This internal oscillator can be adjusted in software by
writing to the OSCTUNE register (Register 5-3). Since
all HFINTOSC clock sources are derived from the
16 MHz internal oscillator a change in the OSCTUNE
register value will apply to all HFINTOSC frequencies.
The default value of the OSCTUNE register is ‘0’. The
value is a 7-bit two’s complement number. A value of
3Fh will provide an adjustment to the maximum
frequency. A value of 40h will provide an adjustment to
the minimum frequency.
When the OSCTUNE register is modified, the oscillator
frequency will begin shifting to the new frequency. Code
execution continues during this shift. There is no
indication that the shift has occurred.
OSCTUNE does not affect the LFINTOSC frequency.
Operation of features that depend on the LFINTOSC
clock source frequency, such as the Power-up Timer
(PWRT), Watchdog Timer (WDT), Fail-Safe Clock
Monitor (FSCM) and peripherals, are not affected by the
change in frequency.
5.2.2.3 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
register. See Section 5.2.2.4 “Internal Oscillator
Frequency Selection” 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
register = 1x), or when any of the following are
enabled:
• Configure the IRCF<3:0> bits of the OSCCON
register for the desired LF frequency, and
• 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.
PIC16(L)F1454/5/9
5.2.2.4
Internal Oscillator Frequency
Selection
The system clock speed can be selected via software
using the Internal Oscillator Frequency Select bits
IRCF<3:0> of the OSCCON register.
The output of the 16 MHz HFINTOSC and 31 kHz
LFINTOSC connects to a postscaler and multiplexer
(see Figure 5-1). The Internal Oscillator Frequency
Select bits IRCF<3:0> of the OSCCON register select
the frequency output of the internal oscillators. One of
the following frequencies can be selected via software:
• HFINTOSC
- 48 MHz (requires 3x PLL)
- 32 MHz (requires 4x PLL)
- 24 MHz (requires 3x PLL)
- 16 MHz
- 8 MHz
- 4 MHz
- 2 MHz
- 1 MHz
- 500 kHz (Default after Reset)
- 250 kHz
- 125 kHz
- 62.5 kHz
- 31.25 kHz
• LFINTOSC
- 31 kHz
Note:
Following any Reset, the IRCF<3:0> bits
of the OSCCON register are set to ‘0111’
and the frequency selection is set to
500 kHz. The user can modify the IRCF
bits to select a different frequency.
The IRCF<3:0> bits of the OSCCON register allow
duplicate selections for some frequencies. These dupli-
cate choices can offer system design trade-offs. Lower
power consumption can be obtained when changing
oscillator sources for a given frequency. Faster transi-
tion times can be obtained between frequency changes
that use the same oscillator source.
 2012 Microchip Technology Inc.
Preliminary
DS41639A-page 63