PIC16F1934_11 Datasheet, PDF (72/472 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers

PIC16(L)F1934/6/7
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 and a dedicated Phase-Lock Loop, HFPLL
that can produce one of three internal system clock
sources.
1. The HFINTOSC (High-Frequency Internal
Oscillator) is factory calibrated and operates at
16 MHz. The HFINTOSC source is generated
from the 500 kHz MFINTOSC source and the
dedicated Phase-Lock Loop, HFPLL. The
frequency of the HFINTOSC can be
user-adjusted via software using the OSCTUNE
register (Register 5-3).
2. The MFINTOSC (Medium-Frequency Internal
Oscillator) is factory calibrated and operates at
500 kHz. The frequency of the MFINTOSC can
be user-adjusted via software using the
OSCTUNE register (Register 5-3).
3. 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
frequency of the HFINTOSC can be altered via
software using the OSCTUNE register (Register 5-3).
The output of the HFINTOSC connects to a postscaler
and multiplexer (see Figure 5-1). One of nine
frequencies derived from the HFINTOSC can be
selected via software using the IRCF<3:0> bits of the
OSCCON register. See Section 5.2.2.7 “Internal
Oscillator Clock Switch Timing” for more information.
The HFINTOSC is enabled by:
• Configure the IRCF<3:0> bits of the OSCCON
register for the desired HF frequency, and
• 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 Locked
bit (HFIOFL) of the OSCSTAT register indicates when
the HFINTOSC is running within 2% of its final value.
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 MFINTOSC
The Medium-Frequency Internal Oscillator
(MFINTOSC) is a factory calibrated 500 kHz internal
clock source. The frequency of the MFINTOSC can be
altered via software using the OSCTUNE register
(Register 5-3).
The output of the MFINTOSC connects to a postscaler
and multiplexer (see Figure 5-1). One of nine
frequencies derived from the MFINTOSC can be
selected via software using the IRCF<3:0> bits of the
OSCCON register. See Section 5.2.2.7 “Internal
Oscillator Clock Switch Timing” for more information.
The MFINTOSC is enabled by:
• Configure the IRCF<3:0> bits of the OSCCON
register for the desired HF frequency, and
• FOSC<2:0> = 100, or
• Set the System Clock Source (SCS) bits of the
OSCCON register to ‘1x’
The Medium-Frequency Internal Oscillator Ready bit
(MFIOFR) of the OSCSTAT register indicates when the
MFINTOSC is running and can be utilized.
DS41364E-page 72
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