Datasheet

 1998-2013 Microchip Technology Inc. DS30292D-page 121
PIC16F87X
12.2 Oscillator Configurations
12.2.1 OSCILLATOR TYPES
The PIC16F87X 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 Low Power Crystal
• XT Crystal/Resonator
• HS High Speed Crystal/Resonator
• RC Resistor/Capacitor
12.2.2 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 12-1). The
PIC16F87X 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 12-2).
FIGURE 12-1: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
FIGURE 12-2: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
TABLE 12-1: CERAMIC RESONATORS
Note 1: See Table 12-1 and Table 12-2 for recom-
mended values of C1 and C2.
2: A series resistor (R
s
) may be required for AT
strip cut crystals.
3: RF varies with the crystal chosen.
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
RF
(3)
SLEEP
To
Logic
PIC16F87X
R
s
(2)
Internal
Ranges Tested:
Mode Freq. OSC1 OSC2
XT 455 kHz
2.0 MHz
4.0 MHz
68 - 100 pF
15 - 68 pF
15 - 68 pF
68 - 100 pF
15 - 68 pF
15 - 68 pF
HS 8.0 MHz
16.0 MHz
10 - 68 pF
10 - 22 pF
10 - 68 pF
10 - 22 pF
These values are for design guidance only.
See notes following Table 12-2.
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.
OSC1
OSC2
Open
Clock from
Ext. System
PIC16F87X