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PIC16(L)F1508/9
DS40001609E-page 46
2011-2015 Microchip Technology Inc.
5.0
OSCILLATOR MODULE (WITH
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 perfor-
mance 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, 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.
• Fail-Safe Clock Monitor (FSCM) designed to
detect a failure of the external clock source (LP,
XT, HS, ECH, ECM, ECL or EXTRC modes) and
switch automatically to the internal oscillator.
• Oscillator Start-up Timer (OST) ensures stability
of crystal oscillator sources
• Fast start-up oscillator allows internal circuits to
power-up and stabilize before switching to the 16
MHz HFINTOSC
The oscillator module can be configured in one of the
following clock modes.
1.
ECL – External Clock Low-Power mode
(0 MHz to 0.5 MHz)
2.
ECM – External Clock Medium Power mode
(0.5 MHz to 4 MHz)
3.
ECH – External Clock High-Power mode
(4 MHz to 20 MHz)
4.
LP – 32 kHz Low-Power Crystal mode.
5.
XT – Medium Gain Crystal or Ceramic Resonator
Oscillator mode (up to 4 MHz)
6.
HS – High Gain Crystal or Ceramic Resonator
mode (4 MHz to 20 MHz)
7.
EXTRC – External Resistor-Capacitor
8.
INTOSC – Internal oscillator (31 kHz to 16 MHz)
Clock Source modes are selected by the FOSC<2:0>
bits in the Configuration Words. The FOSC bits
determine the type of oscillator that will be used when
the device is first powered.
The ECH, ECM, and ECL clock modes rely 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 EXTRC clock mode requires an external resistor
and capacitor to set the oscillator frequency.
The INTOSC internal oscillator block produces a low
and high-frequency clock source, designated
LFINTOSC and HFINTOSC. (See Internal Oscillator
Block,
). A wide selection of device clock
frequencies may be derived from these two clock
sources.
Содержание PIC12F1501
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