Microchip Technology DM164134 Scheda Tecnica
© 2006 Microchip Technology Inc.
DS41159E-page 17
PIC18FXX8
2.0
OSCILLATOR
CONFIGURATIONS
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).
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
PLL enabled
5.
RC
External Resistor/Capacitor
6.
RCIO
External Resistor/Capacitor with I/O
pin enabled
pin enabled
7.
EC
External Clock
8.
ECIO
External Clock with I/O pin enabled
2.2
Crystal Oscillator/Ceramic
Resonators
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.
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.
parallel cut crystal.
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP OSC
CONFIGURATION)
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.
quency out of the crystal manufacturer’s
specifications.
Ranges Tested:
Mode
Freq
OSC1
OSC2
XT
455 kHz
2.0 MHz
4.0 MHz
4.0 MHz
68-100 pF
15-68 pF
15-68 pF
15-68 pF
68-100 pF
15-68 pF
15-68 pF
15-68 pF
HS
8.0 MHz
16.0 MHz
10-68 pF
10-22 pF
10-22 pF
10-68 pF
10-22 pF
10-22 pF
These values are for design guidance only.
See notes following Table 2-2.
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
R
F
(3)
Sleep
To
Logic
PIC18FXX8
R
S
(2)
Internal