Datasheet
1999-2013 Microchip Technology Inc. DS41106C-page 53
PIC16C712/716
9.2 Oscillator Configurations
9.2.1 OSCILLATOR TYPES
The PIC16CXXX can be operated in four different
Oscillator 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
9.2.2 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 9-2). The
PIC16CXXX 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 9-3).
FIGURE 9-2: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
FIGURE 9-3: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
TABLE 9-1: CERAMIC RESONATORS
TABLE 9-2: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
Note 1: See Table 9- 1 and Table 9-2 for
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
PIC16C7XX
RS
(2)
internal
OSC1
OSC2
Open
Clock from
ext. system
PIC16C7XX
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 at bottom of page.
Osc Type
Crystal
Freq
Cap. Range
C1
Cap. Range
C2
LP 32 kHz 33 pF 33 pF
200 kHz 15 pF 15 pF
XT 200 kHz 47-68 pF 47-68 pF
1 MHz 15 pF 15 pF
4 MHz 15 pF 15 pF
HS 4 MHz 15 pF 15 pF
8 MHz 15-33 pF 15-33 pF
20 MHz 15-33 pF 15-33 pF
These values are for design guidance only. See
notes at bottom of page.
Note 1: Recommended values of C1 and C2 are
identical to the ranges tested (Table 9-1).
2: Higher capacitance increases the stability
of the oscillator, but also increases the
start-up time.
3: Since each resonator/crystal has its own
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate values of external compo-
nents.
4: Rs may be required in HS mode, as well
as XT mode to avoid overdriving crystals
with low drive level specification.