PIC16F872
11.2
Oscillator Configurations
TABLE 11-1: CERAMIC RESONATORS
Ranges Tested:
11.2.1
OSCILLATOR TYPES
Mode
Freq
OSC1
OSC2
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:
XT
455 kHz
2.0 MHz
4.0 MHz
68 - 100 pF 68 - 100 pF
15 - 68 pF
15 - 68 pF
15 - 68 pF
15 - 68 pF
• LP
• XT
• HS
• RC
Low Power Crystal
HS
8.0 MHz
16.0 MHz
10 - 68 pF
10 - 22 pF
10 - 68 pF
10 - 22 pF
Crystal/Resonator
These values are for design guidance only. See
notes at bottom of page.
High Speed Crystal/Resonator
Resistor/Capacitor
Resonators Used:
11.2.2 CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
455 kHz Panasonic EFO-A455K04B
± 0.3%
± 0.5%
± 0.5%
± 0.5%
± 0.5%
2.0 MHz
4.0 MHz
8.0 MHz
Murata Erie CSA2.00MG
Murata Erie CSA4.00MG
Murata Erie CSA8.00MT
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).
16.0 MHz Murata Erie CSA16.00MX
All resonators used did not have built-in capacitors.
FIGURE 11-1: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
(1)
C1
OSC1
To
internal
logic
XTAL
(3)
RF
OSC2
SLEEP
PIC16F872
(2)
RS
(1)
C2
Note 1: See Table 11-1 and Table 11-2 for rec-
ommended 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.
FIGURE 11-2: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
OSC1
OSC2
Clock from
ext. system
PIC16F872
Open
1999 Microchip Technology Inc.
Preliminary
DS30221A-page 97
MICROCHIP [ MICROCHIP ]
