Datasheet
2012 Microchip Technology Inc. Preliminary DS41639A-page 61
PIC16(L)F1454/5/9
5.2.1.4 3x PLL or 4x PLL
The oscillator module contains a PLL that can be used
with both external and internal clock sources to provide a
system clock source. By setting the SPLLMULT bit of the
OSCCON register, 3x PLL is selected. By clearing the
SPLLMULT bit of the OSCCON register, 4x PLL is
selected. The input frequency for the PLL must fall within
specifications. See the PLL Clock Timing Specifications in
Section 29.0 “Electrical Specifications”.
The PLL may be enabled for use by one of two methods:
1. Program the PLLEN bit in Configuration Words
to a ‘1’.
2. Write the SPLLEN bit in the OSCCON register to
a ‘1’. If the PLLEN bit in Configuration Words is
programmed to a ‘1’, then the value of SPLLEN
is ignored.
5.2.1.5 Secondary Oscillator
The secondary oscillator is a separate crystal oscillator
that is associated with the Timer1 peripheral. It is opti-
mized for timekeeping operations with a 32.768 kHz
crystal connected between the SOSCO and SOSCI
device pins.
The secondary oscillator can be used as an alternate
system clock source and can be selected during
run-time using clock switching. Refer to Section 5.3
“CPU Clock Divider” for more information.
FIGURE 5-5: QUARTZ CRYSTAL
OPERATION
(SECONDARY
OSCILLATOR)
PLL
HFINTOSC
(MHz)
ECH/HS
(MHz)
System
Clock (MHz)
4x 8 8 - 12 32 - 48
3x 16, 8 8 - 16 24 - 48
C1
C2
32.768 kHz
SOSCI
To Internal
Logic
PIC
®
MCU
Crystal
SOSCO
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.
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 Applications 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)
• AN1288, “Design Practices for
Low-Power External Oscillators”
(DS01288)