PIC16C505T-20I/SL データシートの表示（PDF） - Microchip Technology
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PIC16C505T-20I/SL Datasheet PDF : 85 Pages
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PIC16C505
7.2 Oscillator Configurations
7.2.1 OSCILLATOR TYPES
The PIC16C505 can be operated in four different
oscillator modes. The user can program three
configuration bits (FOSC<2:0>) to select one of these
four modes:
• LP: Low Power Crystal
• XT: Crystal/Resonator
• HS: High Speed Crystal/Resonator
• INTRC: Internal 4 MHz Oscillator
• EXTRC: External Resistor/Capacitor
7.2.2 CRYSTAL OSCILLATOR / CERAMIC
RESONATORS
In HS, XT or LP modes, a crystal or ceramic resonator
is connected to the RB5/OSC1/CLKIN and RB4/
OSC2/CLKOUT pins to establish oscillation
(Figure 7-1). The PIC16C505 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 HS, XT
or LP modes, the device can have an external clock
source drive the RB5/OSC1/CLKIN pin (Figure 7-2).
FIGURE 7-1:
C1(1)
CRYSTAL OPERATION (OR
CERAMIC RESONATOR)
(HS, XT OR LP OSC
CONFIGURATION)
OSC1
PIC16C505
XTAL
RS(2) OSC2
C2(1)
RF(3)
SLEEP
To internal
logic
Note 1:
2:
3:
See Capacitor Selection tables for
recommended values of C1 and C2.
A series resistor (RS) may be required for AT
strip cut crystals.
RF approx. value = 10 MΩ.
FIGURE 7-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
Clock from
ext. system
Open
OSC1
PIC16C505
OSC2
TABLE 7-1:
CAPACITOR SELECTION
FOR CERAMIC RESONATORS
- PIC16C505
Osc Resonator Cap. Range Cap. Range
Type
Freq
C1
C2
XT
4.0 MHz
30 pF
30 pF
HS
16 MHz
10-47 pF
10-47 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.
TABLE 7-2:
CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR -
PIC16C505
Osc Resonator Cap.Range Cap. Range
Type
Freq
C1
C2
LP
32 kHz(1)
15 pF
15 pF
XT
200 kHz 47-68 pF
47-68 pF
1 MHz
15 pF
15 pF
4 MHz
15 pF
15 pF
HS
20 MHz
15-47 pF
15-47 pF
Note 1: For VDD > 4.5V, C1 = C2 ≈ 30 pF is
recommended.
These values are for design guidance only. Rs may
be required to avoid overdriving crystals with low
drive level specification. Since each crystal has its
own characteristics, the user should consult the crys-
tal manufacturer for appropriate values of external
components.
DS40192C-page 28
© 1999 Microchip Technology Inc.
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