
2001 Microchip Technology Inc.
DS30292C-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
Internal
Logic
PIC16F87X
R
s
(2)
Ranges Tested:
Mode
Freq.
OSC1
OSC2
XT
455 kHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
68 - 100 pF
15 - 68 pF
15 - 68 pF
10 - 68 pF
10 - 22 pF
68 - 100 pF
15 - 68 pF
15 - 68 pF
10 - 68 pF
10 - 22 pF
HS
These values are for design guidance only.
See notes following Table 12-2.
Resonators Used:
455 kHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
All resonators used did not have built-in capacitors.
Panasonic EFO-A455K04B
Murata Erie CSA2.00MG
Murata Erie CSA4.00MG
Murata Erie CSA8.00MT
Murata Erie CSA16.00MX
±
0.3%
±
0.5%
±
0.5%
±
0.5%
±
0.5%
OSC1
OSC2
Open
Clock from
Ext. System
PIC16F87X