Datasheet

© 2006 Microchip Technology Inc. DS41159E-page 17
PIC18FXX8
2.0 OSCILLATOR
CONFIGURATIONS
2.1 Oscillator Types
The PIC18FXX8 can be operated in one of eight oscil-
lator modes, programmable by three configuration bits
(FOSC2, FOSC1 and FOSC0).
1. LP Low-Power Crystal
2. XT Crystal/Resonator
3. HS High-Speed Crystal/Resonator
4. HS4 High-Speed Crystal/Resonator with
PLL enabled
5. RC External Resistor/Capacitor
6. RCIO External Resistor/Capacitor with I/O
pin enabled
7. EC External Clock
8. ECIO External Clock with I/O pin enabled
2.2 Crystal Oscillator/Ceramic
Resonators
In XT, LP, HS or HS4 (PLL) 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. An external clock source may also
be connected to the OSC1 pin, as shown in Figure 2-3
and Figure 2-4.
The PIC18FXX8 oscillator design requires the use of a
parallel cut crystal.
FIGURE 2-1: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP OSC
CONFIGURATION)
TABLE 2-1: CERAMIC RESONATORS
Note: Use of a series cut crystal may give a fre-
quency out of the crystal manufacturer’s
specifications.
Ranges Tested:
Mode Freq OSC1 OSC2
XT 455 kHz
2.0 MHz
4.0 MHz
68-100 pF
15-68 pF
15-68 pF
68-100 pF
15-68 pF
15-68 pF
HS 8.0 MHz
16.0 MHz
10-68 pF
10-22 pF
10-68 pF
10-22 pF
These values are for design guidance only.
See notes following Table 2-2.
Resonators Used:
455 kHz Panasonic EFO-A455K04B ±0.3%
2.0 MHz Murata Erie CSA2.00MG ±0.5%
4.0 MHz Murata Erie CSA4.00MG ±0.5%
8.0 MHz Murata Erie CSA8.00MT ±0.5%
16.0 MHz Murata Erie CSA16.00MX ±0.5%
All resonators used did not have built-in capacitors.
Note 1: See Table 2-1 and Table 2-2 for recommended
values of C1 and C2.
2: A series resistor (R
S) may be required for AT
strip cut crystals.
3: R
F varies with the crystal chosen.
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
RF
(3)
Sleep
To
Logic
PIC18FXX8
RS
(2)
Internal