![Microchip Technology PIC12F1501 Скачать руководство пользователя страница 47](http://html1.mh-extra.com/html/microchip-technology/pic12f1501/pic12f1501_manual_1785833047.webp)
PIC16(L)F1508/9
DS40001609E-page 48
2011-2015 Microchip Technology Inc.
5.2
Clock Source Types
Clock sources can be classified as external, internal or
peripheral.
External clock sources rely on external circuitry for the
clock source to function. Examples are: oscillator mod-
ules (ECH, ECM, ECL modes), quartz crystal resona-
tors or ceramic resonators (LP, XT and HS modes) and
Resistor-Capacitor (EXTRC) mode circuits.
Internal clock sources are contained within the oscillator
module. The internal oscillator block has two internal
oscillators that are used to generate the internal system
clock sources: the 16 MHz High-Frequency Internal
Oscillator (HFINTOSC) and the 31 kHz Low-Frequency
Internal Oscillator (LFINTOSC).
The peripheral clock source is a nominal 600 kHz
internal RC oscillator, FRC. The FRC is traditionally
used with the ADC module, but is sometimes available
to other peripherals. See
The system clock can be selected between external or
internal clock sources via the System Clock Select
(SCS) bits in the OSCCON register. See
for additional information.
5.2.1
EXTERNAL CLOCK SOURCES
An external clock source can be used as the device
system clock by performing one of the following
actions:
• Program the FOSC<2:0> bits in the Configuration
Words to select an external clock source that will
be used as the default system clock upon a
device Reset.
• Write the SCS<1:0> bits in the OSCCON register
to switch the system clock source to:
- Secondary oscillator during run-time, or
- An external clock source determined by the
value of the FOSC bits.
See
for more informa-
tion.
5.2.1.1
EC Mode
The External Clock (EC) mode allows an externally
generated logic level signal to be the system clock
source. When operating in this mode, an external clock
source is connected to the OSC1 input.
OSC2/CLKOUT is available for general purpose I/O or
CLKOUT.
shows the pin connections for EC
mode.
EC mode has three power modes to select from through
the F
OSC
bits in the Configuration Words:
• ECH – High-power, 4-20 MHz
• ECM – Medium-power, 0.5-4 MHz
• ECL – Low-power, 0-0.5 MHz
The Oscillator Start-up Timer (OST) is disabled when
EC mode is selected. Therefore, there is no delay in
operation after a Power-on Reset (POR) or wake-up
from Sleep. Because the PIC
®
MCU design is fully
static, stopping the external clock input will have the
effect of halting the device while leaving all data intact.
Upon restarting the external clock, the device will
resume operation as if no time had elapsed.
FIGURE 5-2:
EXTERNAL CLOCK (EC)
MODE OPERATION
5.2.1.2
LP, XT, HS Modes
The LP, XT and HS modes support the use of quartz
crystal resonators or ceramic resonators connected to
OSC1 and OSC2 (
). The three modes select
a low, medium or high gain setting of the internal
inverter-amplifier to support various resonator types
and speed.
LP
Oscillator mode selects the lowest gain setting of the
internal inverter-amplifier. LP mode current consumption
is the least of the three modes. This mode is designed to
drive only 32.768 kHz tuning-fork type crystals (watch
crystals).
XT
Oscillator mode selects the intermediate gain
setting of the internal inverter-amplifier. XT mode
current consumption is the medium of the three modes.
This mode is best suited to drive resonators with a
medium drive level specification.
HS
Oscillator mode selects the highest gain setting of the
internal inverter-amplifier. HS mode current consumption
is the highest of the three modes. This mode is best
suited for resonators that require a high drive setting.
and
show typical circuits for
quartz crystal and ceramic resonators, respectively.
Clock from
Ext. system
F
OSC
/4 or I/O
(1)
OSC1/CLKIN
PIC
®
MCU
OSC2/CLKOUT
Note 1:
Output depends upon the CLKOUTEN bit
of the Configuration Words.
Rev. 10-000045A
7/30/2013
Содержание PIC12F1501
Страница 307: ...PIC16 L F1508 9 DS40001609E page 308 2011 2015 Microchip Technology Inc NOTES...
Страница 392: ...2011 2015 Microchip Technology Inc DS40001609E page 393 PIC16 L F1508 9 1RWH 6 7 7 588 8 7...
Страница 399: ...PIC16 L F1508 9 DS40001609E page 400 2011 2015 Microchip Technology Inc NOTES...