Datasheet

 2002 Microchip Technology Inc. DS30325B-page 91
PIC16F7X
12.2 Oscillator Configurations
12.2.1 OSCILLATOR TYPES
The PIC16F7X 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
PIC16F7X oscillator design requires the use of a parallel
cut crystal. Use of a series cut crystal may give a fre-
quency out of the crystal manufacturers specifications.
When in HS mode, the device can accept an external
clock source to drive the OSC1/CLKIN pin (Figure 12-2).
See Figure 15-1 or Figure 15-2 (depending on the part
number and V
DD range) for valid external clock
frequencies.
FIGURE 12-1: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
FIGURE 12-2: EXTERNAL CLOCK INPUT
OPERATION (HS OSC
CONFIGURATION)
TABLE 12-1: CERAMIC RESONATORS
(FOR DESIGN GUIDANCE
ONLY)
Note 1: See Table 12-1 and Table 12-2 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.
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
RF
(3)
SLEEP
To
Logic
PIC16F7X
RS
(2)
Internal
Typical Capacitor Values Used:
Mode Freq OSC1 OSC2
XT 455 kHz
2.0 MHz
4.0 MHz
56 pF
47 pF
33 pF
56 pF
47 pF
33 pF
HS 8.0 MHz
16.0 MHz
27 pF
22 pF
27 pF
22 pF
Capacitor values are for design guidance only.
These capacitors were tested with the resonators
listed below for basic start-up and operation. These
values were not optimized.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
V
DD and temperature range for the application.
See the notes at the bottom of page 92 for additional
information.
Resonators Used:
455 kHz Panasonic EFO-A455K04B
2.0 MHz Murata Erie CSA2.00MG
4.0 MHz Murata Erie CSA4.00MG
8.0 MHz Murata Erie CSA8.00MT
16.0 MHz Murata Erie CSA16.00MX
OSC1
OSC2
Open
Clock from
Ext. System
PIC16F7X
(HS Mode)