PIC12F629/675
FIGURE 9-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT, EC,
OR LP OSC
9.2
Oscillator Configurations
9.2.1
OSCILLATOR TYPES
CONFIGURATION)
The PIC±2F629/675 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
PIC12F629/675
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 GP4 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 PICmicroTM
Ranges Characterized:
Mid-Range
(DS33023).
Reference
Manual,
Mode
Freq
OSC1(C1)
OSC2(C2)
XT
455 kHz
2.0 MHz
4.0 MHz
68 - ±00 pF
±5 - 68 pF
±5 - 68 pF
68 - ±00 pF
±5 - 68 pF
±5 - 68 pF
9.2.2
CRYSTAL OSCILLATOR / CERAMIC
RESONATORS
In XT, LP or HS modes a crystal or ceramic resonator
is connected to the OSC± and OSC2 pins to establish
oscillation (see Figure 9-±). The PIC±2F629/675
oscillator 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
OSC± pin (see Figure 9-2).
HS
8.0 MHz
±6.0 MHz
±0 - 68 pF
±0 - 22 pF
±0 - 68 pF
±0 - 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
components.
FIGURE 9-1:
CRYSTAL OPERATION (OR
CERAMIC RESONATOR)
HS, XT OR LP OSC
TABLE 9-2:
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
CONFIGURATION
Mode
Freq
OSC1(C1)
OSC2(C2)
OSC1
LP
32 kHz
68 - ±00 pF
68 - ±00 pF
To Internal
Logic
C1(1)
XT
HS
±00 kHz
2 MHz
4 MHz
68 - ±50 pF ±50 - 200 pF
±5 - 30 pF
±5 - 30 pF
XTAL
±5 - 30 pF
±5 - 30 pF
SLEEP
RF(3)
OSC2
RS(2)
8 MHz
±0 MHz
20 MHz
±5 - 30 pF
±5 - 30 pF
±5 - 30 pF
±5 - 30 pF
±5 - 30 pF
±5 - 30 pF
C2(1)
PIC12F629/675
Note 1: See Table 9-1 and Table 9-2 for recommended
values of C1 and C2.
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
2: A series resistor may be required for AT strip cut
crystals.
3: RF varies with the Oscillator mode selected
(Approx. value = 10 MΩ).
components.
2003 Microchip Technology Inc.
DS41190C-page 53
MICROCHIP [ MICROCHIP ]
