PIC16F630/676
FIGURE 9-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT, EC,
OR LP OSC
9.2
Oscillator Configurations
9.2.1
OSCILLATOR TYPES
CONFIGURATION)
The PIC16F630/676 can be operated in eight different
Oscillator Option modes. The user can program three
configuration bits (FOSC2 through FOSC0) to select
one of these eight modes:
Clock from
External System
OSC1
PIC16F630/676
OSC2(1)
• LP
• XT
• HS
• RC
Low Power Crystal
Open
Crystal/Resonator
High Speed Crystal/Resonator
External Resistor/Capacitor (2 modes)
Note 1: Functions as RA4 in EC Osc mode.
• INTOSC Internal Oscillator (2 modes)
• EC External Clock In
TABLE 9-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Note: Additional information on oscillator config-
urations is available in the PIC® Mid-Range
Reference Manual, (DS33023).
Ranges Characterized:
Mode
Freq
OSC1(C1)
OSC2(C2)
9.2.2
CRYSTAL OSCILLATOR / CERAMIC
RESONATORS
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
In XT, LP or HS modes a crystal or ceramic resonator
is connected to the OSC1 and OSC2 pins to establish
oscillation (see Figure 9-1). The PIC16F630/676 oscil-
lator design requires the use of a parallel cut crystal.
Use of a series cut crystal may yield a frequency
outside of the crystal manufacturers specifications.
When in XT, LP or HS modes, the device can have an
external clock source to drive the OSC1 pin (see
Figure 9-2).
HS
8.0 MHz
16.0 MHz
10 - 68 pF
10 - 22 pF
10 - 68 pF
10 - 22 pF
Note 1: Higher capacitance increases the stability
of the oscillator but also increases the
start-up time. These values are for design
guidance only. Since each resonator has
its own characteristics, the user should
consult the resonator manufacturer for
appropriate values of external
FIGURE 9-1:
CRYSTAL OPERATION (OR
CERAMIC RESONATOR)
(HS, XT OR LP OSC
components.
TABLE 9-2:
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
CONFIGURATION)
OSC1
Mode
Freq
OSC1(C1)
OSC2(C2)
To Internal
Logic
C1(1)
LP
32 kHz
68 - 100 pF
68 - 100 pF
XTAL
XT
HS
100 kHz
2 MHz
4 MHz
68 - 150 pF 150 - 200 pF
SLEEP
RF(3)
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
OSC2
RS(2)
C2(1)
PIC16F630/676
8 MHz
10 MHz
20 MHz
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
Note 1: See Table 9-1 and Table 9-2 for recommended
values of C1 and C2.
2: A series resistor may be required for AT strip cut
crystals.
3: RF varies with the Oscillator mode selected
(Approx. value = 10 MΩ).
Note 1: Higher capacitance increases the stability
of the oscillator but also increases the
start-up time. These values are for design
guidance only. Rs may be required in HS
mode as well as XT mode to avoid
overdriving crystals with low drive level
specification. Since each crystal has its
own characteristics, the user should
consult the crystal manufacturer for
appropriate values of external
components.
© 2007 Microchip Technology Inc.
DS40039E-page 55
MICROCHIP [ MICROCHIP ]
