PIC16C65A/JW View Datasheet(PDF) - Microchip Technology
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PIC16C65A/JW Datasheet PDF : 108 Pages
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9.2 Oscillator Configurations
9.2.1 OSCILLATOR TYPES
The PIC16C62X 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 9-2). 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 9-3).
FIGURE 9-2:
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 9-3:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
Clock from
ext. system
Open
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
16.0 MHz
10 - 22 pF
10 - 68 pF
10 - 22 pF
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 man-
ufacturer for appropriate values of external components.
TABLE 9-2: CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR
Mode
Freq
OSC1(C1)
OSC2(C2)
LP
32 kHz
200 kHz
68 - 100 pF
15 - 30 pF
68 - 100 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 manu-
facturer for appropriate values of external components.
© 1998 Microchip Technology Inc.
Preliminary
DS30235G-page 47
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