PIC18C658 MICROCHIP [Microchip Technology], PIC18C658 Datasheet - Page 23

• Manufacturer Part Number: PIC18C658
• Description: High-Performance Microcontrollers with CAN Module
• Manufacturer: MICROCHIP [Microchip Technology]

2.3
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
ues and the operating temperature. In addition to this,
the oscillator frequency will vary from unit to unit due
to normal process parameter 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 2-2 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 2-2:
The RCIO oscillator mode functions like the RC 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).
 2000 Microchip Technology Inc.
C
V
Recommended values:
R
EXT
SS
EXT
V
DD
RC Oscillator
F
or I/O
OSC
RC OSCILLATOR MODE
/4
EXT
OSC1
OSC2/CLKO/RA6
EXT
values. The user also needs to
3 k Ω ≤ R
C
EXT
) and capacitor (C
> 20pF
EXT
≤ 100 k Ω
PIC18CXX8
Advanced Information
Internal
clock
EXT
) val-
2.4
The EC and ECIO oscillator modes require an external
clock source to be connected to the OSC1 pin. The
feedback device between OSC1 and OSC2 is turned
off in these modes to save current. There is no oscilla-
tor start-up time required after a Power-on Reset or
after a recovery 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
External Clock Input
F
RA6
OSC
EXTERNAL CLOCK INPUT
OPERATION
(EC OSC CONFIGURATION)
EXTERNAL CLOCK INPUT
OPERATION
(ECIO CONFIGURATION)
/4
PIC18CXX8
OSC1
OSC2
OSC1
I/O (OSC2)
PIC18CXX8
PIC18CXX8
DS30475A-page 23