PIC18F2220/2320/4220/4320
2.0
2.1
OSCILLATOR
CONFIGURATIONS
Oscillator Types
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
OSC1
To
Internal
Logic
Sleep
The PIC18F2X20 and PIC18F4X20 devices can be
operated in ten different oscillator modes. The user can
program the configuration bits, F
OSC
3:F
OSC
0, in
Configuration Register 1H to select one of these ten
modes:
1.
2.
3.
4.
5.
6.
7.
8.
LP
XT
HS
HSPLL
RC
RCIO
INTIO1
INTIO2
Low-Power Crystal
Crystal/Resonator
High-Speed Crystal/Resonator
High-Speed Crystal/Resonator
with PLL enabled
External Resistor/Capacitor with
F
OSC
/4 output on RA6
External Resistor/Capacitor with
I/O on RA6
Internal Oscillator with F
OSC
/4
output on RA6 and I/O on RA7
Internal Oscillator with I/O on RA6
and RA7
External Clock with F
OSC
/4 output
External Clock with I/O on RA6
C1
(1)
XTAL
R
S
(2)
C2
(1)
Note 1:
2:
3:
OSC2
R
F
(3)
PIC18FXXXX
See Table 2-1 and Table 2-2 for initial values
of C1 and C2.
A series resistor (R
S
) may be required for AT
strip cut crystals.
R
F
varies with the oscillator mode chosen.
TABLE 2-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Typical Capacitor Values Used:
Mode
XT
Freq
455 kHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
OSC1
56 pF
47 pF
33 pF
27 pF
22 pF
OSC2
56 pF
47 pF
33 pF
27 pF
22 pF
9. EC
10. ECIO
2.2
Crystal Oscillator/Ceramic
Resonators
HS
In XT, LP, HS or HSPLL Oscillator modes, a crystal or
ceramic resonator is connected to the OSC1 and
OSC2 pins to establish oscillation. Figure 2-1 shows
the pin connections.
The oscillator design requires the use of a parallel cut
crystal.
Note:
Use of a series cut crystal may give a fre-
quency out of the crystal manufacturers
specifications.
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.
Different capacitor values may be required to produce
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 on page 20 for additional information.
Resonators Used:
455 kHz
2.0 MHz
16.0 MHz
4.0 MHz
8.0 MHz
2003 Microchip Technology Inc.
DS39599C-page 19
MICROCHIP [ MICROCHIP TECHNOLOGY ]
