PIC18F2221 MICROCHIP [Microchip Technology], PIC18F2221 Datasheet - Page 25

• Manufacturer Part Number: PIC18F2221
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

2.0
2.1
The PIC18F4321 family of 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.
© 2007 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
frequency 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
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
to the following application notes for oscillator specific
information:
• AN588, “PIC
• AN826, “Crystal Oscillator Basics and Crystal
• AN849, “Basic PIC
• AN943, “Practical PIC
• AN949, “Making Your Oscillator Work”
See the notes following Table 2-2 for additional
information.
PIC18F4321 FAMILY
DD
Note:
Note 1: See Table 2-1 and Table 2-2 for initial values of
Mode
Guide”
Selection for rfPIC
Design”
XT
and temperature range for the application. Refer
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 may be placed
between the OSC2 pin and the resonator.
As
recommended value of R
F
3.58 MHz
XTAL
R
varies with the oscillator mode chosen.
S
®
Freq
(2)
Microcontroller Oscillator Design
a
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
OSC2
OSC1
®
®
good
CRYSTAL/CERAMIC
RESONATOR OPERATION
(XT, LP, HS OR HSPLL
CONFIGURATION)
and PIC
Oscillator Design”
®
Oscillator Analysis and
S
OSC1
22 pF
) may be required for AT
R
starting
®
F
(3)
Devices”
DS39689E-page 23
S
PIC18FXXXX
is 330Ω.
Sleep
point,
To
OSC2
22 pF
Internal
Logic
DD
the
for