2002 Microchip Technology Inc.
Preliminary
DS30453D-page 15
PIC16C5X
4.0
OSCILLATOR
CONFIGURATIONS
4.1
Oscillator Types
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:
1.
LP:
Low Power Crystal
2.
XT:
Crystal/Resonator
3.
HS:
High Speed Crystal/Resonator
4.
RC:
Resistor/Capacitor
4.2
Crystal Oscillator/Ceramic
Resonators
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1/CLKIN and OSC2/CLKOUT
pins
to
establish
oscillation
The
PIC16C5X oscillator design requires the use of a paral-
lel cut crystal. Use of a series cut crystal may give a fre-
quency out of the crystal manufacturers specifications.
When in XT, LP or HS modes, the device can have an
external clock source drive the OSC1/CLKIN pin
FIGURE 4-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP OSC
CONFIGURATION)
FIGURE 4-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
TABLE 4-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS -
PIC16C5X, PIC16CR5X
TABLE 4-2:
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR -
PIC16C5X, PIC16CR5X
Note:
Not all oscillator selections available for all
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.
3: RF varies with the Oscillator mode cho-
sen (approx. value = 10 M
).
C1(1)
C2(1)
XTAL
OSC2
OSC1
RF(3)
SLEEP
To internal
logic
RS(2)
PIC16C5X
Osc
Type
Resonator
Freq
Cap. Range
C1
Cap. Range
C2
XT
455 kHz
2.0 MHz
4.0 MHz
68-100 pF
15-33 pF
10-22 pF
68-100 pF
15-33 pF
10-22 pF
HS
8.0 MHz
16.0 MHz
10-22 pF
10 pF
10-22 pF
10 pF
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.
Osc
Type
Crystal
Freq
Cap.Range
C1
Cap. Range
C2
LP
32 kHz(1)
15 pF
XT
100 kHz
200 kHz
455 kHz
1 MHz
2 MHz
4 MHz
15-30 pF
15 pF
200-300 pF
100-200 pF
15-100 pF
15-30 pF
15 pF
HS
4 MHz
8 MHz
20 MHz
15 pF
Note 1: For VDD > 4.5V, C1 = C2
≈ 30 pF is
recommended.
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 characteris-
tics in your application.
Clock from
ext. system
OSC1
OSC2
PIC16C5X
Open