Microchip Technology AC244045 Data Sheet
2010-2012 Microchip Technology Inc.
DS41440C-page 55
PIC16(L)F1825/1829
5.0
OSCILLATOR MODULE (WITH
FAIL-SAFE CLOCK MONITOR)
FAIL-SAFE CLOCK MONITOR)
5.1
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
performance and minimizing power consumption.
sources and selection features that allow it to be used
in a wide range of applications while maximizing
performance and minimizing power consumption.
illustrates a block diagram of the oscillator
module.
Clock sources can be supplied from external oscillators,
quartz crystal resonators, ceramic resonators and
Resistor-Capacitor (RC) circuits. In addition, the system
clock source can be supplied from one of two internal
oscillators and PLL circuits, with a choice of speeds
selectable via software. Additional clock features
include:
• Selectable system clock source between external
Clock sources can be supplied from external oscillators,
quartz crystal resonators, ceramic resonators and
Resistor-Capacitor (RC) circuits. In addition, the system
clock source can be supplied from one of two internal
oscillators and PLL circuits, 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 oscillator module can be configured in one of eight
clock modes.
1.
clock modes.
1.
ECL – External Clock Low-Power mode
(0 MHz to 0.5 MHz)
(0 MHz to 0.5 MHz)
2.
ECM – External Clock Medium-Power mode
(0.5 MHz to 4 MHz)
(0.5 MHz to 4 MHz)
3.
ECH – External Clock High-Power mode
(4 MHz to 32 MHz)
(4 MHz to 32 MHz)
4.
LP – 32 kHz Low-Power Crystal mode.
5.
XT – Medium Gain Crystal or Ceramic Resonator
Oscillator mode (up to 4 MHz)
Oscillator mode (up to 4 MHz)
6.
HS – High Gain Crystal or Ceramic Resonator
mode (4 MHz to 20 MHz)
mode (4 MHz to 20 MHz)
7.
RC – External Resistor-Capacitor (RC).
8.
INTOSC – Internal oscillator (31 kHz to 32 MHz).
Clock Source modes are selected by the FOSC<2:0>
bits in the Configuration Word 1. The FOSC bits
determine the type of oscillator that will be used when
the device is first powered.
The EC clock mode relies on an external logic level
signal as the device clock source. The LP, XT and HS
clock modes require an external crystal or resonator to
be connected to the device. Each mode is optimized for
a different frequency range. The RC clock mode
requires an external resistor and capacitor to set the
oscillator frequency.
The INTOSC internal oscillator block produces low,
medium, and high frequency clock sources, designated
LFINTOSC, MFINTOSC, and HFINTOSC. (see
Internal Oscillator Block,
bits in the Configuration Word 1. The FOSC bits
determine the type of oscillator that will be used when
the device is first powered.
The EC clock mode relies on an external logic level
signal as the device clock source. The LP, XT and HS
clock modes require an external crystal or resonator to
be connected to the device. Each mode is optimized for
a different frequency range. The RC clock mode
requires an external resistor and capacitor to set the
oscillator frequency.
The INTOSC internal oscillator block produces low,
medium, and high frequency clock sources, designated
LFINTOSC, MFINTOSC, and HFINTOSC. (see
Internal Oscillator Block,
). A wide selection
of device clock frequencies may be derived from these
three clock sources.
three clock sources.