© 2008 Microchip Technology Inc.
PIC18F2525/2620/4525/4620 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:
HSPLL High-Speed Crystal/Resonator
with PLL Enabled
External Resistor/Capacitor with
FOSC/4 Output on RA6
External Resistor/Capacitor with I/O
INTIO1 Internal Oscillator with FOSC/4 Output
on RA6 and I/O on RA7
INTIO2 Internal Oscillator with I/O on RA6
External Clock with FOSC/4 Output
External Clock with I/O on RA6
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
(XT, LP, HS OR HSPLL
CAPACITOR SELECTION FOR
Use of a series cut crystal may give a fre-
quency out of the crystal manufacturer’s
Typical Capacitor Values Used:
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
VDD and temperature range for the application.
See the notes following Table 2-2 for additional
See Table 2-1 and Table 2-2 for initial values of
C1 and C2.
A series resistor (RS) may be required for AT
strip cut crystals.
RF varies with the oscillator mode chosen.