PIC18FXX8 Datasheet, PDF (19/402 Pages) Microchip Technology – 28/40-Pin High-Performance, Enhanced Flash Microcontrollers with CAN Module

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
2. XT
3. HS
4. HS4
5. RC
6. RCIO
7. EC
8. ECIO
Low-Power Crystal
Crystal/Resonator
High-Speed Crystal/Resonator
High-Speed Crystal/Resonator with
PLL enabled
External Resistor/Capacitor
External Resistor/Capacitor with I/O
pin enabled
External Clock
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.
Note:
Use of a series cut crystal may give a fre-
quency out of the crystal manufacturer’s
specifications.
PIC18FXX8
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP OSC
CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
RF⁽³⁾
To
Internal
Logic
RS⁽²⁾
C2⁽¹⁾
OSC2
Sleep
PIC18FXX8
Note 1: See Table 2-1 and Table 2-2 for recommended
values of C1 and C2.
2: A series resistor (RS) may be required for AT
strip cut crystals.
3: RF varies with the crystal chosen.
TABLE 2-1: CERAMIC RESONATORS
Ranges Tested:
Mode
Freq
OSC1
OSC2
XT
455 kHz 68-100 pF 68-100 pF
2.0 MHz
15-68 pF 15-68 pF
4.0 MHz
15-68 pF 15-68 pF
HS
8.0 MHz
10-68 pF 10-68 pF
16.0 MHz 10-22 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.
 2004 Microchip Technology Inc.
DS41159D-page 17