PIC12C5XX
8.2
Oscillator Configurations
OSCILLATOR TYPES
TABLE 8-1:
CAPACITOR SELECTION
FOR CERAMIC RESONATORS
- PIC12C5XX
8.2.1
The PIC12C5XX can be operated in four different
oscillator modes. The user can program two
configuration bits (FOSC1:FOSC0) to select one of
these four modes:
Osc
Type
Resonator Cap. Range Cap. Range
Freq
C1
C2
XT
4.0 MHz
30 pF
30 pF
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.
• LP:
• XT:
Low Power Crystal
Crystal/Resonator
• INTRC: Internal 4 MHz Oscillator
• EXTRC: External Resistor/Capacitor
TABLE 8-2:
CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR -
PIC12C5XX
8.2.2
CRYSTAL OSCILLATOR / CERAMIC
RESONATORS
Osc
Resonator Cap.Range Cap. Range
In XT or LP modes, a crystal or ceramic resonator is
connected to the GP5/OSC1/CLKIN and GP4/OSC2
pins to establish oscillation (Figure 8-2). The
PIC12C5XX oscillator design requires the use of a
parallel cut crystal. Use of a series cut crystal may give
Type
Freq
C1
C2
(1)
LP
XT
32 kHz
15 pF
15 pF
200 kHz
1 MHz
4 MHz
47-68 pF
15 pF
15 pF
47-68 pF
15 pF
15 pF
a
frequency out of the crystal manufacturers
Note 1: For VDD > 4.5V, C1 = C2 ≈ 30 pF is
recommended.
specifications. When in XT or LP modes, the device
can have an external clock source drive the GP5/
OSC1/CLKIN pin (Figure 8-3).
These values are for design guidance only. Rs may
be required to avoid overdriving crystals with low
drive level specification. Since each crystal has its
own characteristics, the user should consult the crys-
tal manufacturer for appropriate values of external
components.
FIGURE 8-2: CRYSTAL OPERATION (OR
CERAMIC RESONATOR) (XT
OR LP OSC
CONFIGURATION)
C1(1)
OSC1
PIC12C5XX
SLEEP
XTAL
RF(3)
To internal
logic
OSC2
RS(2)
C2(1)
Note 1: See Capacitor Selection tables for
recommended values of C1 and C2.
2: A series resistor (RS) may be required for
AT strip cut crystals.
3: RF approximate value = 10 MΩ.
FIGURE 8-3: EXTERNAL CLOCK INPUT
OPERATION (XT OR LP OSC
CONFIGURATION)
OSC1
PIC12C5XX
OSC2
Clock from
ext. system
Open
DS40139E-page 36
1999 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
