Microchip Technology DM183021 Data Sheet
2010 Microchip Technology Inc.
DS39616D-page 29
PIC18F2331/2431/4331/4431
3.0
OSCILLATOR
CONFIGURATIONS
CONFIGURATIONS
3.1
Oscillator Types
The PIC18F2331/2431/4331/4431 devices can be
operated in 10 different oscillator modes. The user can
program the Configuration bits, FOSC<3:0>, in
Configuration Register 1H to select one of these
10 modes:
1.
operated in 10 different oscillator modes. The user can
program the Configuration bits, FOSC<3:0>, in
Configuration Register 1H to select one of these
10 modes:
1.
LP
Low-Power Crystal
2.
XT
Crystal/Resonator
3.
HS
High-Speed Crystal/Resonator
4.
HSPLL
High-Speed Crystal/Resonator
with PLL Enabled
with PLL Enabled
5.
RC
External Resistor/Capacitor with
F
OSC
/4 Output on RA6
6.
RCIO
External Resistor/Capacitor with
I/O on RA6
7.
INTIO1
Internal Oscillator with F
OSC
/4
Output on RA6 and I/O on RA7
8.
INTIO2
Internal Oscillator with I/O on RA6
and RA7
and RA7
9.
EC
External Clock with F
OSC
/4 Output
10. ECIO
External Clock with I/O on RA6
3.2
Crystal Oscillator/Ceramic
Resonators
Resonators
In XT, LP, HS or HSPLL Oscillator modes, a crystal or
ceramic resonator is connected to the OSC1 and
OSC2 pins to establish oscillation.
ceramic resonator is connected to the OSC1 and
OSC2 pins to establish oscillation.
shows
the pin connections.
The oscillator design requires the use of a parallel
resonant crystal.
The oscillator design requires the use of a parallel
resonant crystal.
FIGURE 3-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
TABLE 3-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
CERAMIC RESONATORS
Note:
Use of a series resonant crystal may give
a frequency out of the crystal
manufacturers’ specifications.
a frequency out of the crystal
manufacturers’ specifications.
Typical Capacitor Values Used:
Mode
Freq
OSC1
OSC2
XT
455 kHz
2.0 MHz
4.0 MHz
4.0 MHz
56 pF
47 pF
33 pF
47 pF
33 pF
56 pF
47 pF
33 pF
47 pF
33 pF
HS
8.0 MHz
16.0 MHz
27 pF
22 pF
22 pF
27 pF
22 pF
22 pF
Capacitor values are for design guidance only.
These capacitors were tested with the resonators
listed below for basic start-up and operation. These
values are not optimized
listed below for basic start-up and operation. These
values are not optimized
.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
V
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
V
DD
and temperature range for the application.
See the notes following
for additional
information.
Resonators Used:
455 kHz
4.0 MHz
2.0 MHz
8.0 MHz
16.0 MHz
Note 1:
See
for initial values of
C1 and C2.
2:
A series resistor (R
S
) may be required for AT
strip resonant crystals.
3:
R
F
varies with the oscillator mode chosen.
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
R
F(3)
Sleep
To
Logic
PIC18FXXXX
R
S(2)
Internal