PIC16C5X
7.2
Oscillator Configurations
FIGURE 7-4: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
7.2.1
OSCILLATOR TYPES
OSC CONFIGURATION)
PIC16C5Xs can be operated in four different oscillator
modes. The user can program two configuration bits
(FOSC1:FOSC0) to select one of these four modes:
OSC1
OSC2
Clock from
ext. system
PIC16C5X
• LP:
• XT:
• HS:
• RC:
Low Power Crystal
Open
Crystal/Resonator
High Speed Crystal/Resonator
Resistor/Capacitor
TABLE 7-1:
CAPACITOR SELECTION
FOR CERAMIC RESONATORS
- PIC16C5X, PIC16CR5X
Note: Not all oscillator selections available for all
parts. See Section 7.1.
Osc
Type
Resonator Cap. Range Cap. Range
7.2.2
CRYSTAL OSCILLATOR / CERAMIC
RESONATORS
Freq
C1
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
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1/CLKIN and OSC2/CLKOUT
pins to establish oscillation (Figure 7-3). The
PIC16C5X oscillator design requires the use of a
parallel cut crystal. Use of a series cut crystal may give
HS
4.0 MHz
8.0 MHz
16.0 MHz
15-68 pF
10-68 pF
10-22 pF
15-68 pF
10-68 pF
10-22 pF
a
frequency out of the crystal manufacturers
Note: These values are for design guidance only.
Since each resonator has its own charac-
teristics, the user should consult the reso-
nator manufacturer for appropriate values
of external components.
specifications. When in XT, LP or HS modes, the
device can have an external clock source drive the
OSC1/CLKIN pin (Figure 7-4).
FIGURE 7-3: CRYSTAL OPERATION
(OR CERAMIC RESONATOR)
(HS, XT OR LP OSC
TABLE 7-2:
CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR
- PIC16C5X, PIC16CR5X
CONFIGURATION)
(1)
C1
Osc
Type
Resonator Cap.Range Cap. Range
OSC1
PIC16C5X
Freq
C1
C2
(1)
SLEEP
LP
32 kHz
15 pF
15 pF
XTAL
(3)
RF
100 kHz
200 kHz
15-30 pF
15-30 pF
30-47 pF
15-82 pF
To internal
logic
OSC2
(2)
XT
100 kHz
200 kHz
455 kHz
1 MHz
2 MHz
4 MHz
15-30 pF
15-30 pF
15-30 pF
15-30 pF
15-30 pF
15-47 pF
200-300 pF
100-200 pF
15-100 pF
15-30 pF
15-30 pF
15-47 pF
RS
(1)
C2
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.
HS
4 MHz
8 MHz
20 MHz
15-30 pF
15-30 pF
15-30 pF
15-30 pF
15-30 pF
15-30 pF
3: RF varies with the crystal chosen (approx.
value = 10 MΩ).
Note 1: For VDD > 4.5V, C1 = C2 ≈ 30 pF is
recommended.
2: 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.
Note: If you change from this device to
another device, please verify oscillator
characteristics in your application.
1998 Microchip Technology Inc.
Preliminary
DS30453B-page 33
MICROCHIP [ MICROCHIP ]
