
2003 Microchip Technology Inc.
DS30569B-page 89
PIC16F870/871
11.2
Oscillator Configurations
11.2.1
OSCILLATOR TYPES
The PIC16F870/871 can be operated in four different
Oscillator modes. The user can program two configura-
tion 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
11.2.2
CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1/CLKI and OSC2/CLKO pins
871 oscillator design requires the use of a parallel cut
crystal. Use of a series cut crystal may give a frequency
out of the crystal manufacturers specifications. When in
XT, LP or HS modes, the device can have an external
FIGURE 11-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
FIGURE 11-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
TABLE 11-1:
CERAMIC RESONATORS
Note
1:
recommended 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.
C1(1)
C2(1)
XTAL
OSC2
OSC1
RF(3)
SLEEP
To
Logic
PIC16F870/871
Rs
(2)
Internal
Ranges Tested:
Mode
Freq.
OSC1
OSC2
XT
455 kHz
2.0 MHz
4.0 MHz
68 - 100 pF
15 - 68 pF
68 - 100 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.
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
PIC16F870/871