PIC18F6585 Datasheet, PDF (25/496 Pages) Microchip Technology – 64/68/80-Pin High-Performance, 64-Kbyte Enhanced Flash Microcontrollers with ECAN Module

PIC18F6585/8585/6680/8680
2.0 OSCILLATOR
CONFIGURATIONS
2.1 Oscillator Types
The PIC18F6585/8585/6680/8680 devices can be
operated in eleven different oscillator modes. The user
can program four configuration bits (FOSC3, FOSC2,
FOSC1 and FOSC0) to select one of these eleven
modes:
1. LP
Low-Power Crystal
2. XT
Crystal/Resonator
3. HS
High-Speed Crystal/Resonator
4. RC
External Resistor/Capacitor
5. EC
External Clock
6. ECIO
External Clock with I/O
pin enabled
7. HS+PLL
High-Speed Crystal/Resonator
with PLL enabled
8. RCIO
External Resistor/Capacitor with
I/O pin enabled
9. ECIO+SPLL External Clock with software
controlled PLL
10. ECIO+PLL External Clock with PLL and I/O
pin enabled
11. HS+SPLL High-Speed Crystal/Resonator
with software control
2.2 Crystal Oscillator/Ceramic
Resonators
In XT, LP, HS, HS+PLL or HS+SPLL 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 PIC18F6585/8585/6680/8680 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 manufacturers
specifications.
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
RF⁽³⁾
To
Internal
Logic
RS⁽²⁾
C2⁽¹⁾
OSC2
Sleep
PIC18FXX80/XX85
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 oscillator mode chosen.
TABLE 2-1: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Ranges Tested:
Mode
Freq
C1
C2
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 this table.
Resonators Used:
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: Higher capacitance increases the stability
of the oscillator, but also increases the
start-up time.
2: When operating below 3V VDD, or when
using certain ceramic resonators at any
voltage, it may be necessary to use high
gain HS mode, try a lower frequency
resonator, or switch to a crystal oscillator.
3: Since each resonator/crystal has its own
characteristics, the user should consult the
resonator/crystal manufacturer for appro-
priate values of external components, or
verify oscillator performance.
 2004 Microchip Technology Inc.
DS30491C-page 23