PIC16C62X
9.2
Oscillator Configurations
TABLE 9-1:
CAPACITOR SELECTION
FOR CERAMIC RESONATORS
9.2.1
OSCILLATOR TYPES
Ranges Characterized:
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:
Mode
Freq
OSC1(C1)
OSC2(C2)
XT
455 kHz
2.0 MHz
4.0 MHz
22 - 100 pF
15 - 68 pF
15 - 68 pF
22 - 100 pF
15 - 68 pF
15 - 68 pF
• LP
• XT
• HS
• RC
Low Power Crystal
Crystal/Resonator
HS
8.0 MHz
10 - 68 pF
10 - 22 pF
10 - 68 pF
10 - 22 pF
16.0 MHz
High Speed Crystal/Resonator
Resistor/Capacitor
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.
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).
TABLE 9-2:
CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR
Mode
Freq
OSC1(C1)
OSC2(C2)
32 kHz
68 - 100 pF
15 - 30 pF
68 - 100 pF
15 - 30 pF
LP
200 kHz
100 kHz
2 MHz
4 MHz
68 - 150 pF
15 - 30 pF
15 - 30 pF
150 - 200 pF
15 - 30 pF
15 - 30 pF
XT
HS
FIGURE 9-2: CRYSTAL OPERATION
(OR CERAMIC RESONATOR)
(HS, XT OR LP OSC
8 MHz
10 MHz
20 MHz
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
CONFIGURATION)
OSC1
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.
To internal logic
C1
XTAL
RS
SLEEP
RF
OSC2
see Note
C2
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
OSC1
PIC16C62X
OSC2
Open
1998 Microchip Technology Inc.
Preliminary
DS30235G-page 47
MICROCHIP [ MICROCHIP ]
