PIC18F2420 MICROCHIP [Microchip Technology], PIC18F2420 Datasheet - Page 26

• Manufacturer Part Number: PIC18F2420
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F2420/2520/4420/4520
TABLE 2-2:
DS39631A-page 24
Osc Type
Capacitor values are for design guidance only.
These capacitors were tested with the crystals listed
below for basic start-up and operation. These values
are not optimized.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
V
See the notes following this table for additional
information.
DD
Note 1: Higher capacitance increases the stability
XT
HS
LP
and temperature range for the application.
2: When operating below 3V V
3: Since each resonator/crystal has its own
4: Rs may be required to avoid overdriving
5: Always verify oscillator performance over
25 MHz
32 kHz
1 MHz
of the oscillator but also increases the
start-up time.
using certain ceramic resonators at any
voltage, it may be necessary to use the
HS mode or switch to a crystal oscillator.
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate
components.
crystals with low drive level specification.
the V
expected for the application.
Crystal
10 MHz
20 MHz
25 MHz
25 MHz
32 kHz
1 MHz
4 MHz
4 MHz
Freq
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
DD
Crystals Used:
and temperature range that is
Typical Capacitor Values
values
30 pF
15 pF
15 pF
15 pF
15 pF
15 pF
15 pF
0 pF
C1
Tested:
10 MHz
20 MHz
4 MHz
of
DD
, or when
30 pF
15 pF
15 pF
15 pF
15 pF
15 pF
15 pF
5 pF
external
C2
Preliminary
An external clock source may also be connected to the
OSC1 pin in the HS mode, as shown in Figure 2-2.
FIGURE 2-2:
2.3
The EC and ECIO Oscillator modes require an external
clock source to be connected to the OSC1 pin. There is
no oscillator start-up time required after a Power-on
Reset or after an exit from Sleep mode.
In the EC Oscillator mode, the oscillator frequency
divided by 4 is available on the OSC2 pin. This signal
may be used for test purposes or to synchronize other
logic. Figure 2-3 shows the pin connections for the EC
Oscillator mode.
FIGURE 2-3:
The ECIO Oscillator mode functions like the EC mode,
except that the OSC2 pin becomes an additional gen-
eral purpose I/O pin. The I/O pin becomes bit 6 of
PORTA (RA6). Figure 2-4 shows the pin connections
for the ECIO Oscillator mode.
FIGURE 2-4:
Clock from
Ext. System
Clock from
Ext. System
Clock from
Ext. System
External Clock Input
F
RA6
Open
OSC
/4
EXTERNAL CLOCK INPUT
OPERATION (HS OSC
CONFIGURATION)
EXTERNAL CLOCK
INPUT OPERATION
(EC CONFIGURATION)
EXTERNAL CLOCK
INPUT OPERATION
(ECIO CONFIGURATION)
 2004 Microchip Technology Inc.
OSC1/CLKI
I/O (OSC2)
OSC1/CLKI
OSC2/CLKO
OSC1
OSC2
PIC18FXXXX
PIC18FXXXX
PIC18FXXXX
(HS Mode)