Microchip Technology MA160014 Data Sheet
2010-2012 Microchip Technology Inc.
DS41412E-page 27
PIC18(L)F2X/4XK22
2.0
OSCILLATOR MODULE (WITH
FAIL-SAFE CLOCK MONITOR)
FAIL-SAFE CLOCK MONITOR)
2.1
Overview
The oscillator module has a wide variety of clock
sources and selection features that allow it to be used
in a wide range of applications while maximizing perfor-
mance and minimizing power consumption.
sources and selection features that allow it to be used
in a wide range of applications while maximizing perfor-
mance and minimizing power consumption.
illustrates a block diagram of the oscillator module.
Clock sources can be configured from external
oscillators, quartz crystal resonators, ceramic resonators
and Resistor-Capacitor (RC) circuits. In addition, the
system clock source can be configured from one of three
internal oscillators, with a choice of speeds selectable via
software. Additional clock features include:
oscillators, quartz crystal resonators, ceramic resonators
and Resistor-Capacitor (RC) circuits. In addition, the
system clock source can be configured from one of three
internal oscillators, with a choice of speeds selectable via
software. Additional clock features include:
• Selectable system clock source between external
or internal sources via software.
• Two-Speed Start-up mode, which minimizes
latency between external oscillator start-up and
code execution.
code execution.
• Fail-Safe Clock Monitor (FSCM) designed to
detect a failure of the external clock source (LP,
XT, HS, EC or RC modes) and switch
automatically to the internal oscillator.
XT, HS, EC or RC modes) and switch
automatically to the internal oscillator.
• Oscillator Start-up Timer (OST) ensures stability
of crystal oscillator sources.
The primary clock module can be configured to provide
one of six clock sources as the primary clock.
one of six clock sources as the primary clock.
1.
RC
External Resistor/Capacitor
2.
LP Low-Power Crystal
3.
XT
Crystal/Resonator
4.
INTOSC Internal Oscillator
5.
HS
High-Speed Crystal/Resonator
6.
EC
External Clock
The HS and EC oscillator circuits can be optimized for
power consumption and oscillator speed using settings
in FOSC<3:0>. Additional FOSC<3:0> selections
enable RA6 to be used as I/O or CLKO (F
power consumption and oscillator speed using settings
in FOSC<3:0>. Additional FOSC<3:0> selections
enable RA6 to be used as I/O or CLKO (F
OSC
/4) for
RC, EC and INTOSC Oscillator modes.
Primary Clock modes are selectable by the
FOSC<3:0> bits of the CONFIG1H Configuration
register. The primary clock operation is further defined
by these Configuration and register bits:
FOSC<3:0> bits of the CONFIG1H Configuration
register. The primary clock operation is further defined
by these Configuration and register bits:
1.
PRICLKEN (CONFIG1H<5>)
2.
PRISD (OSCCON2<2>)
3.
PLLCFG (CONFIG1H<4>)
4.
PLLEN (OSCTUNE<6>)
5.
HFOFST (CONFIG3H<3>)
6.
IRCF<2:0> (OSCCON<6:4>)
7.
MFIOSEL (OSCCON2<4>)
8.
INTSRC (OSCTUNE<7>)
The HFINTOSC, MFINTOSC and LFINTOSC are
factory calibrated high, medium and low-frequency
oscillators, respectively, which are used as the internal
clock sources.
factory calibrated high, medium and low-frequency
oscillators, respectively, which are used as the internal
clock sources.