PIC18F2331 MICROCHIP [Microchip Technology], PIC18F2331 Datasheet - Page 25

• Manufacturer Part Number: PIC18F2331
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D
• Manufacturer: MICROCHIP [Microchip Technology]

2.4
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 2-4 shows the pin connections for the EC
Oscillator mode.
FIGURE 2-4:
The ECIO Oscillator mode functions like the EC mode,
except that the OSC2 pin becomes an additional
general purpose I/O pin. The I/O pin becomes bit 6 of
PORTA (RA6). Figure 2-5 shows the pin connections
for the ECIO Oscillator mode.
FIGURE 2-5:
 2003 Microchip Technology Inc.
Clock from
Ext. System
Clock from
Ext. System
External Clock Input
F
RA6
OSC
/4
EXTERNAL CLOCK INPUT
OPERATION
(EC CONFIGURATION)
EXTERNAL CLOCK INPUT
OPERATION
(ECIO CONFIGURATION)
OSC1/CLKI
OSC2/CLKO
OSC1/CLKI
I/O (OSC2)
PIC18FXXXX
PIC18FXXXX
PIC18F2331/2431/4331/4431
Preliminary
2.5
For timing insensitive applications, the “RC” and
“RCIO” device options offer additional cost savings.
The RC oscillator frequency is a function of the supply
voltage, the resistor (R
values and the operating temperature. In addition to
this, the oscillator frequency will vary from unit to unit
due to normal manufacturing variation. Furthermore,
the difference in lead frame capacitance between
package types will also affect the oscillation frequency,
especially for low C
take into account variation due to tolerance of external
R and C components used. Figure 2-6 shows how the
R/C combination is connected.
In the RC 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 2-6:
The RCIO Oscillator mode (Figure 2-7) functions like
the RC mode, except that the OSC2 pin becomes an
additional general purpose I/O pin. The I/O pin
becomes bit 6 of PORTA (RA6).
FIGURE 2-7:
C
V
C
V
Recommended values: 3 k
Recommended values: 3 k
R
R
EXT
SS
EXT
SS
EXT
EXT
V
V
DD
DD
RC Oscillator
RA6
F
OSC
EXT
/4
RC OSCILLATOR MODE
OSC1
RCIO OSCILLATOR MODE
OSC1
OSC2/CLKO
I/O (OSC2)
values. The user also needs to
C
C
EXT
EXT
EXT
> 20 pF
> 20 pF
) and capacitor (C
R
R
EXT
EXT
DS39616B-page 23
100 k
100 k
PIC18FXXXX
PIC18FXXXX
Internal
Internal
Clock
Clock
EXT
)