PIC18LF24K Datasheet, PDF (45/594 Pages) –

PIC18(L)F26/45/46K40
4.3.1.5 Secondary Oscillator
The secondary oscillator is a separate oscillator block
that can be used as an alternate system clock source.
The secondary oscillator is optimized for 32.768 kHz,
and can be used with an external crystal oscillator con-
nected to the SOSCI and SOSCO device pins, or an
external clock source connected to the SOSCIN pin.
The secondary oscillator can be selected during
run-time using clock switching. Refer to Section
4.4 “Clock Switching” for more information.
FIGURE 4-5:
QUARTZ CRYSTAL
OPERATION
(SECONDARY
OSCILLATOR)
PIC^® MCU
SOSCI
C1
32.768 kHz
Quartz
Crystal
To Internal
Logic
C2
SOSCO
Note 1: Quartz crystal characteristics vary
according to type, package and
manufacturer. The user should consult the
manufacturer data sheets for specifications
and recommended application.
2: Always verify oscillator performance over
the VDD and temperature range that is
expected for the application.
3: For oscillator design assistance, reference
the following Microchip Application Notes:
• AN826, “Crystal Oscillator Basics and
Crystal Selection for PIC^® and PIC^®
Devices” (DS00826)
• AN849, “Basic PIC^® Oscillator Design”
(DS00849)
• AN943, “Practical PIC^® Oscillator
Analysis and Design” (DS00943)
• AN949, “Making Your Oscillator Work”
(DS00949)
• TB097, “Interfacing a Micro Crystal
MS1V-T1K 32.768 kHz Tuning Fork
Crystal to a PIC16F690/SS” (DS91097)
• AN1288, “Design Practices for
Low-Power External Oscillators”
(DS01288)
4.3.2 INTERNAL CLOCK SOURCES
The device may be configured to use the internal
oscillator block as the system clock by performing one
of the following actions:
• Program the RSTOSC<2:0> 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 NOSC<2:0> bits in the OSCCON1
register to switch the system clock source to the
internal oscillator during run-time. See Section
4.4 “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 CLKOUTEN bit in Configuration Words.
The internal oscillator block has two independent
oscillators that can produce two internal system clock
sources.
1. The HFINTOSC (High-Frequency Internal
Oscillator) is factory-calibrated and operates
from 1 to 64 MHz. The frequency of HFINTOSC
can be selected through the OSCFRQ
Frequency Selection register, and fine-tuning
can be done via the OSCTUNE register.
2. The LFINTOSC (Low-Frequency Internal
Oscillator) is factory-calibrated and operates at
31 kHz.
 2016 Microchip Technology Inc.
Preliminary
DS40001816C-page 45