PIC16C84_13 Datasheet, PDF (36/110 Pages) Microchip Technology – 8-bit CMOS EEPROM Microcontroller

PIC16C84
8.2 Oscillator Configurations
8.2.1 OSCILLATOR TYPES
The PIC16C84 can be operated in four different
oscillator modes. 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
8.2.2 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 (Figure 8-2).
FIGURE 8-2:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP OSC
CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
OSC2
RS⁽²⁾
C2⁽¹⁾
RF⁽³⁾
To
internal
logic
SLEEP
PIC16CXX
Note1:
2:
3:
See Table 8-1 and Table 8-2 for recom-
mended values of C1 and C2.
A series resistor (RS) may be required for
AT strip cut crystals.
RF varies with the crystal chosen.
The PIC16C84 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/
CLKIN pin (Figure 8-3).
FIGURE 8-3:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
Clock from
ext. system
Open
OSC1
PIC16CXX
OSC2
TABLE 8-1
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Ranges Tested:
Mode
Freq
OSC1/C1 OSC2/C2
XT
455 kHz 47 - 100 pF 47 - 100 pF
2.0 MHz 15 - 33 pF 15 - 33 pF
4.0 MHz 15 - 33 pF 15 - 33 pF
HS
8.0 MHz 15 - 33 pF 15 - 33 pF
10.0 MHz 15 - 33 pF 15 - 33 pF
Note : Recommended values of C1 and C2 are identical to
the ranges tested table.
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 manufacturer for the
appropriate values of external components.
Resonators Tested:
455 kHz Panasonic EFO-A455K04B 0.3%
2.0 MHz Murata Erie CSA2.00MG
0.5%
4.0 MHz Murata Erie CSA4.00MG
0.5%
8.0 MHz Murata Erie CSA8.00MT
 0.5%
10.0 MHz Murata Erie CSA10.00MTZ 0.5%
None of the resonators had built-in capacitors.
TABLE 8-2
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
Mode
Freq
OSC1/C1 OSC2/C2
LP
32 kHz 68 - 100 pF 68 - 100 pF
200 kHz 15 - 33 pF 15 - 33 pF
XT
100 kHz 100 - 150 pF 100 - 150 pF
2 MHz
15 - 33 pF 15 - 33 pF
4 MHz
15 - 33 pF 15 - 33 pF
HS
4 MHz
15 - 33 pF 15 - 33 pF
10 MHz 15 - 33 pF 15 - 33 pF
Note :
Higher capacitance increases the stability of
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 speci-
fication. Since each crystal has its own
characteristics, the user should consult the crystal
manufacturer for appropriate values of external
components.
For VDD > 4.5V, C1 = C2  30 pF is recommended.
Crystals Tested:
32.768 kHz
100 kHz
200 kHz
1.0 MHz
2.0 MHz
4.0 MHz
10.0 MHz
Epson C-001R32.768K-A  20 PPM
Epson C-2 100.00 KC-P  20 PPM
STD XTL 200.000 KHz  20 PPM
ECS ECS-10-13-2
 50 PPM
ECS ECS-20-S-2
 50 PPM
ECS ECS-40-S-4
 50 PPM
ECS ECS-100-S-4
 50 PPM
DS30445D-page 36
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