PIC16F872_06 Datasheet, PDF (91/168 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS Flash Microcontroller with 10-Bit A/D

11.2 Oscillator Configurations
11.2.1 OSCILLATOR TYPES
The PIC16F872 can be operated in four different oscil-
lator modes. The user can program two configuration
bits (FOSC1 and FOSC0) to select one of these four
modes:
• LP
• XT
• HS
• RC
Low Power Crystal
Crystal/Resonator
High Speed Crystal/Resonator
Resistor/Capacitor
11.2.2
CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1/CLKIN and OSC2/CLKOUT
pins to establish oscillation (Figure 11-1). The
PIC16F872 oscillator design requires the use of a par-
allel cut crystal. Use of a series cut crystal may give a
frequency out of the crystal manufacturers specifica-
tions. When in XT, LP or HS modes, the device can
have an external clock source to drive the OSC1/
CLKIN pin (Figure 11-2).
FIGURE 11-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
C2⁽¹⁾
OSC2
RS⁽²⁾
RF⁽³⁾
To
Internal
Logic
SLEEP
PIC16F87X
Note 1: See Table 11-1 and Table 11-2 for recom-
mended values of C1 and C2.
2: A series resistor (RS) may be required for
AT strip cut crystals.
3: RF varies with the crystal chosen.
PIC16F872
FIGURE 11-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
Clock from
Ext. System
Open
OSC1
PIC16F87X
OSC2
TABLE 11-1: CERAMIC RESONATORS
Ranges Tested:
Mode
Freq
OSC1
OSC2
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 Table 11-2.
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.
© 2006 Microchip Technology Inc.
DS30221C-page 89