PIC16C554T-IPT View Datasheet(PDF) - Microchip Technology
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PIC16C554T-IPT Datasheet PDF : 108 Pages
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6.2 Oscillator Configurations
6.2.1 OSCILLATOR TYPES
The PIC16C55X 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
6.2.2
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 6-1). The PIC16C55X 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 6-2).
FIGURE 6-1:
CRYSTAL OPERATION
(OR CERAMIC
RESONATOR) (HS, XT OR
LP OSC
CONFIGURATION)
OSC1
C1
XTAL
OSC2
RS
C2 Note 1
To internal logic
RF
SLEEP
PIC16C55X
Note
1: A series resistor may be required for AT strip cut
crystals.
2: See Table 6-1 and Table 6-2 for recommended val-
ues of C1 and C2.
FIGURE 6-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
Clock from
ext. system
Open
OSC1
PIC16C55X
OSC2
PIC16C55X
TABLE 6-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
(PRELIMINARY)
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
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 with the resonator manufacturer for
appropriate values of external compo-
nents.
TABLE 6-2:
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
(PRELIMINARY)
Mode
Freq
OSC1(C1) OSC2(C2)
LP
32 kHz 68 - 100 pF 68 - 100 pF
200 kHz 15 - 30 pF 15 - 30 pF
XT
100 kHz 68 - 150 pF 150 - 200 pF
2 MHz
15 - 30 pF 15 - 30 pF
4 MHz
15 - 30 pF 15 - 30 pF
HS
8 MHz
15 - 30 pF 15 - 30 pF
10 MHz 15 - 30 pF 15 - 30 pF
20 MHz 15 - 30 pF 15 - 30 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. Rs may be required in HS
mode as well as XT mode to avoid over-
driving crystals with low-drive level specifi-
cation. Since each crystal has its own
characteristics, the user should consult
with the crystal manufacturer for appropri-
ate values of external components.
1996-2013 Microchip Technology Inc.
Preliminary
DS40143E-page 33
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