PIC18F2420 MICROCHIP [Microchip Technology], PIC18F2420 Datasheet - Page 25

• Manufacturer Part Number: PIC18F2420
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

2.0
2.1
PIC18F2420/2520/4420/4520 devices can be operated
in ten different oscillator modes. The user can program
the configuration bits, FOSC3:FOSC0, in Configuration
Register 1H to select one of these ten modes:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10. ECIO
2.2
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.
 2004 Microchip Technology Inc.
Note:
LP
XT
HS
HSPLL High-Speed Crystal/Resonator
RC
RCIO
INTIO1 Internal Oscillator with F
INTIO2 Internal Oscillator with I/O on RA6
EC
OSCILLATOR
CONFIGURATIONS
Oscillator Types
Crystal Oscillator/Ceramic
Resonators
Use of a series cut crystal may give a fre-
quency out of the crystal manufacturer’s
specifications.
Low-Power Crystal
Crystal/Resonator
High-Speed Crystal/Resonator
with PLL enabled
External Resistor/Capacitor with
F
External Resistor/Capacitor with I/O
on RA6
on RA6 and I/O on RA7
and RA7
External Clock with F
External Clock with I/O on RA6
OSC
/4 output on RA6
OSC
OSC
/4 output
/4 output
PIC18F2420/2520/4420/4520
Preliminary
FIGURE 2-1:
TABLE 2-1:
Capacitor values are for design guidance only.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
V
See the notes following Table 2-2 for additional
information.
Note 1: See Table 2-1 and Table 2-2 for initial values of
DD
Note:
Mode
XT
and temperature range for the application.
C1
C2
2: A series resistor (R
3: R
(1)
(1)
Typical Capacitor Values Used:
C1 and C2.
strip cut crystals.
When using resonators with frequencies
above 3.5 MHz, the use of HS mode,
rather than XT mode, is recommended.
HS mode may be used at any V
which the controller is rated. If HS is
selected, it is possible that the gain of the
oscillator will overdrive the resonator.
Therefore, a series resistor should be
placed between the OSC2 pin and the
resonator. As a good starting point, the
recommended value of R
F
3.58 MHz
4.19 MHz
XTAL
R
varies with the oscillator mode chosen.
4 MHz
4 MHz
S
Freq
(2)
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
OSC2
OSC1
CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
S
OSC1
) may be required for AT
15 pF
15 pF
30 pF
50 pF
R
F
(3)
DS39631A-page 23
S
PIC18FXXXX
is 330 .
Sleep
To
OSC2
Internal
Logic
15 pF
15 pF
30 pF
50 pF
DD
for