PIC16C622-20/SS View Datasheet(PDF) - Microchip Technology
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PIC16C622-20/SS Datasheet PDF : 128 Pages
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9.2 Oscillator Configurations
9.2.1
OSCILLATOR TYPES
The PIC16C62X devices can be operated in four
different oscillator options. The user can program two
configuration bits (FOSC1 and FOSC0) to select one of
these four modes:
• LP
• XT
• HS
• RC
Low Power Crystal
Crystal/Resonator
High Speed Crystal/Resonator
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 and OSC2 pins to establish
oscillation (Figure 9-1). The PIC16C62X oscillator
design requires the use of a parallel cut crystal. Use of
a series cut crystal may give a frequency out 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 (Figure 9-2).
FIGURE 9-1:
CRYSTAL OPERATION
(OR CERAMIC
RESONATOR) (HS, XT OR
LP OSC
CONFIGURATION)
OSC1
C1
XTAL
OSC2
RS
C2 See Note
To internal logic
RF
SLEEP
PIC16C62X
See Table 9-1 and Table 9-2 for recommended
values of C1 and C2.
Note: A series resistor may be required for
AT strip cut crystals.
FIGURE 9-2:
clock from
ext. system
Open
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
OSC1
PIC16C62X
OSC2
PIC16C62X
TABLE 9-1: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Ranges Characterized:
Mode
Freq
OSC1(C1) OSC2(C2)
XT
455 kHz 22 - 100 pF 22 - 100 pF
2.0 MHz 15 - 68 pF 15 - 68 pF
4.0 MHz 15 - 68 pF 15 - 68 pF
HS
8.0 MHz 10 - 68 pF
10 - 68 pF
16.0 MHz 10 - 22 pF 10 - 22 pF
Higher capacitance increases the stability of the oscil-
lator 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.
TABLE 9-2: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
Mode
Freq
OSC1(C1) OSC2(C2)
LP
32 kHz 68 - 100 pF 68 - 100 pF
200 kHz 15 - 30 pF 15 - 30 pF
100 kHz 68 - 150 pF 150 - 200 pF
XT
2 MHz
15 - 30 pF 15 - 30 pF
4 MHz
15 - 30 pF 15 - 30 pF
8 MHz
15 - 30 pF 15 - 30 pF
HS
10 MHz 15 - 30 pF 15 - 30 pF
20 MHz 15 - 30 pF 15 - 30 pF
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.
2003 Microchip Technology Inc.
DS30235J-page 47
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