PIC18F2331/2431/4331/4431
FIGURE 3-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
3.0
3.1
OSCILLATOR
CONFIGURATIONS
Oscillator Types
(1)
C1
OSC1
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:
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 3-1 and Table 3-2 for initial values of
4. HSPLL
High-Speed Crystal/Resonator
with PLL Enabled
C1 and C2.
2: A series resistor (RS) may be required for AT
5. RC
External Resistor/Capacitor with
FOSC/4 Output on RA6
strip resonant crystals.
3: RF varies with the oscillator mode chosen.
6. RCIO
7. INTIO1
8. INTIO2
External Resistor/Capacitor with
I/O on RA6
TABLE 3-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Internal Oscillator with FOSC/4
Output on RA6 and I/O on RA7
Internal Oscillator with I/O on RA6
and RA7
Typical Capacitor Values Used:
Mode
Freq
OSC1
OSC2
9. EC
External Clock with FOSC/4 Output
External Clock with I/O on RA6
10. ECIO
XT
455 kHz
2.0 MHz
4.0 MHz
56 pF
47 pF
33 pF
56 pF
47 pF
33 pF
3.2
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 3-1 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
resonant 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 resonant crystal may give
frequency out of the crystal
manufacturers’ specifications.
a
See the notes following Table 3-2 for additional
information.
Resonators Used:
455 kHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
2010 Microchip Technology Inc.
DS39616D-page 29
MICROCHIP [ MICROCHIP ]
