PIC18F2331_07 Datasheet, PDF (25/400 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D

PIC18F2331/2431/4331/4431
2.0 OSCILLATOR
CONFIGURATIONS
2.1 Oscillator Types
The PIC18F2331/2431/4331/4431 devices can be
operated in 10 different oscillator modes. The user can
program the Configuration bits FOSC3:FOSC0 in
Configuration Register 1H to select one of these 10
modes:
1. LP
2. XT
3. HS
4. HSPLL
5. RC
6. RCIO
7. INTIO1
8. INTIO2
9. EC
10. ECIO
Low-Power Crystal
Crystal/Resonator
High-Speed Crystal/Resonator
High-Speed Crystal/Resonator
with PLL Enabled
External Resistor/Capacitor with
FOSC/4 Output on RA6
External Resistor/Capacitor with
I/O on RA6
Internal Oscillator with FOSC/4
Output on RA6 and I/O on RA7
Internal Oscillator with I/O on RA6
and RA7
External Clock with FOSC/4 Output
External Clock with I/O on RA6
2.2 Crystal Oscillator/Ceramic
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. 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
frequency out of the crystal
manufacturers’ specifications.
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
RF⁽³⁾
To
Internal
Logic
RS⁽²⁾
C2⁽¹⁾
OSC2
Sleep
PIC18FXXXX
Note 1: See Table 2-1 and Table 2-2 for initial values of
C1 and C2.
2: A series resistor (RS) may be required for AT
strip cut crystals.
3: RF varies with the oscillator mode chosen.
TABLE 2-1: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Typical Capacitor Values Used:
Mode
Freq
OSC1
OSC2
XT
455 kHz
2.0 MHz
4.0 MHz
56 pF
47 pF
33 pF
56 pF
47 pF
33 pF
HS
8.0 MHz
16.0 MHz
27 pF
22 pF
27 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.
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.
See the notes following Table 2-2 for additional
information.
Resonators Used:
455 kHz
2.0 MHz
16.0 MHz
4.0 MHz
8.0 MHz
© 2007 Microchip Technology Inc.
Preliminary
DS39616C-page 23