Microchip Technology AC244045 Data Sheet
2010-2012 Microchip Technology Inc.
DS41440C-page 59
PIC16(L)F1825/1829
5.2.1.4
4xPLL
The oscillator module contains a 4xPLL that can be
used with both external and internal clock sources to
provide a system clock source. The input frequency for
the 4xPLL must fall within specifications. See the PLL
Clock Timing Specifications in
used with both external and internal clock sources to
provide a system clock source. The input frequency for
the 4xPLL must fall within specifications. See the PLL
Clock Timing Specifications in
The 4xPLL may be enabled for use by one of two
methods:
1.
methods:
1.
Program the PLLEN bit in Configuration Word 2
to a ‘1’.
to a ‘1’.
2.
Write the SPLLEN bit in the OSCCON register to
a ‘1’. If the PLLEN bit in Configuration Word 2 is
programmed to a ‘1’, then the value of SPLLEN
is ignored.
a ‘1’. If the PLLEN bit in Configuration Word 2 is
programmed to a ‘1’, then the value of SPLLEN
is ignored.
5.2.1.5
TIMER1 Oscillator
The Timer1 Oscillator is a separate crystal oscillator
that is associated with the Timer1 peripheral. It is
optimized for timekeeping operations with a 32.768
kHz crystal connected between the T1OSO and T1OSI
device pins.
The Timer1 Oscillator can be used as an alternate
system clock source and can be selected during
run-time using clock switching. Refer to
that is associated with the Timer1 peripheral. It is
optimized for timekeeping operations with a 32.768
kHz crystal connected between the T1OSO and T1OSI
device pins.
The Timer1 Oscillator can be used as an alternate
system clock source and can be selected during
run-time using clock switching. Refer to
for more information.
FIGURE 5-5:
QUARTZ CRYSTAL
OPERATION (TIMER1
OSCILLATOR)
OPERATION (TIMER1
OSCILLATOR)
5.2.1.6
External RC Mode
The external Resistor-Capacitor (RC) modes support
the use of an external RC circuit. This allows the
designer maximum flexibility in frequency choice while
keeping costs to a minimum when clock accuracy is not
required.
The RC circuit connects to OSC1. 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 use of an external RC circuit. This allows the
designer maximum flexibility in frequency choice while
keeping costs to a minimum when clock accuracy is not
required.
The RC circuit connects to OSC1. 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.
shows the external RC mode connections.
C1
C2
32.768 kHz
T1OSI
To Internal
Logic
Logic
PIC
®
MCU
Crystal
T1OSO
Quartz
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.
manufacturer. The user should consult the
manufacturer data sheets for specifications
and recommended application.
2: Always verify oscillator performance over
the V
DD
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 rfPIC
®
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)
Crystal to a PIC16F690/SS” (DS91097)
• AN1288, “Design Practices for
Low-Power External Oscillators”
(DS01288)
(DS01288)