PIC18F2220/2320/4220/4320
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOROPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
2.0
2.1
OSCILLATOR
CONFIGURATIONS
Oscillator Types
(1)
C1
OSC1
The PIC18F2X20 and PIC18F4X20 devices can be
operated in ten different oscillator modes. The user can
program the configuration bits, FOSC3:FOSC0, in
Configuration Register 1H to select one of these ten
modes:
To
Internal
Logic
XTAL
(3)
RF
Sleep
(2)
RS
1. LP
Low-Power Crystal
(1)
PIC18FXXXX
C2
2. XT
Crystal/Resonator
OSC2
3. HS
High-Speed Crystal/Resonator
Note 1: See Table 2-1 and Table 2-2 for initial values
of C1 and C2.
4. HSPLL
High-Speed Crystal/Resonator
with PLL enabled
2: A series resistor (RS) may be required for AT
strip cut crystals.
5. RC
External Resistor/Capacitor with
FOSC/4 output on RA6
3: RF varies with the oscillator mode chosen.
6. RCIO
7. INTIO1
8. INTIO2
External Resistor/Capacitor with
I/O on RA6
Internal Oscillator with FOSC/4
output on RA6 and I/O on RA7
TABLE 2-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Internal Oscillator with I/O on RA6
and RA7
Typical Capacitor Values Used:
9. EC
External Clock with FOSC/4 output
External Clock with I/O on RA6
Mode
Freq
OSC1
OSC2
10. ECIO
XT
455 kHz
2.0 MHz
4.0 MHz
56 pF
47 pF
33 pF
56 pF
47 pF
33 pF
2.2
Crystal Oscillator/Ceramic
Resonators
HS
8.0 MHz
16.0 MHz
27 pF
22 pF
27 pF
22 pF
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.
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.
The oscillator design requires the use of a parallel cut
crystal.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application.
Note:
Use of a series cut crystal may give a fre-
quency out of the crystal manufacturers
specifications.
See the notes on page 20 for additional information.
Resonators Used:
455 kHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
2003 Microchip Technology Inc.
DS39599C-page 19
MICROCHIP [ MICROCHIP ]
