PIC16F7X7
TABLE 4-1:
Osc Type
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR (FOR
DESIGN GUIDANCE ONLY)
4.0
4.1
OSCILLATOR
CONFIGURATIONS
Typical Capacitor Values
Oscillator Types
Crystal
Freq
Tested:
The PIC16F7X7 can be operated in eight different oscil-
lator modes. The user can program three configuration
bits (FOSC2:FOSC0) to select one of these eight modes
(modes 5-8 are new PIC16 oscillator configurations):
C1
C2
LP
XT
32 kHz
200 kHz
200 kHz
1 MHz
33 pF
15 pF
56 pF
15 pF
15 pF
15 pF
15 pF
15 pF
33 pF
15 pF
56 pF
15 pF
15 pF
15 pF
15 pF
15 pF
1. LP
2. XT
3. HS
4. RC
Low-Power Crystal
Crystal/Resonator
High-Speed Crystal/Resonator
4 MHz
External Resistor/Capacitor with
FOSC/4 output on RA6
HS
4 MHz
5. RCIO External Resistor/Capacitor with
I/O on RA6
8 MHz
20 MHz
6. INTIO1 Internal Oscillator with FOSC/4
output on RA6 and I/O on RA7
Capacitor values are for design guidance only.
These capacitors were tested with the crystals listed
below for basic start-up and operation. These values
were not optimized.
7. INTIO2 Internal Oscillator with I/O on RA6
and RA7
8. ECIO External Clock with I/O on RA6
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application.
4.2
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
to establish oscillation (see Figure 4-1 and Figure 4-2).
The PIC16F7X7 oscillator design requires the use of a
parallel cut crystal. Use of a series cut crystal may give
See the notes following this table for additional
information.
Note 1: Higher capacitance increases the stability
of oscillator but also increases the
start-up time.
a
frequency out of the crystal manufacturer’s
specifications.
2: Since each crystal has its own character-
istics, the user should consult the crystal
manufacturer for appropriate values of
external components.
FIGURE 4-1:
CRYSTAL OPERATION
(HS, XT OR LP OSC
CONFIGURATION)
3: Rs may be required in HS mode, as well
as XT mode, to avoid overdriving crystals
with low drive level specification.
OSC1
PIC16F7X7
C1(1)
4: Always verify oscillator performance over
the VDD and temperature range that is
expected for the application.
XTAL
OSC2
(3)
RF
Sleep
(2)
RS
C2(1)
To Internal
Logic
Note 1: See Table 4-1 for typical 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 (typically
between 2 MΩ to 10 MΩ).
2004 Microchip Technology Inc.
DS30498C-page 33