Datasheet

 2013-2015 Microchip Technology Inc. DS40001723D-page 47
PIC12(L)F1571/2
5.0 OSCILLATOR MODULE
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. Figure 5-1
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
or internal sources via software
• Oscillator Start-up Timer (OST) ensures stability
of crystal oscillator sources
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 32 MHz)
4. INTOSC – Internal Oscillator (31 kHz to 32 MHz)
Clock Source modes are selected by the FOSC<1:0>
bits in the Configuration Words. The FOSC bits deter-
mine 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 INTOSC internal oscillator block produces low,
medium and high-frequency clock sources, designated
as LFINTOSC, MFINTOSC and HFINTOSC (see
Internal Oscillator Block, Figure 5-1). A wide selection
of device clock frequencies may be derived from these
three clock sources.