PIC18F13K50-E/P MICROCHIP [Microchip Technology], PIC18F13K50-E/P Datasheet - Page 16

• Manufacturer Part Number: PIC18F13K50-E/P
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F1XK50/PIC18LF1XK50
FIGURE 2-3:
2.3.3
The External Resistor-Capacitor (RC) mode supports
the use of an external RC circuit. This allows the
designer maximum flexibility in frequency choice while
keeping costs to a minimum when clock accuracy is not
required. In RC mode, the RC circuit connects to OSC1,
allowing OSC2 to be configured as an IO or as
CLKOUT. The CLKOUT function is selected by the
FOSC bits of the CONFIG1H Configuration register.
When OSC2 is configured as CLKOUT, the frequency
at the pin is the frequency of the RC oscillator divided by
4. Figure 2-4 shows the external RC mode connections.
FIGURE 2-4:
DS41350C-page 14
R
C
Note 1: A series resistor (R
Note 1:
V
Recommended values: 10 kΩ ≤ R
EXT
EXT
SS
V
F
I/O
C1
C2 Ceramic
DD
OSC
2: The value of R
3: An additional parallel feedback resistor (R
(2)
2:
/4 or
Resonator
ceramic resonators with low drive level.
selected (typically between 2 MΩ to 10 MΩ).
may be required for proper ceramic resonator
operation.
EXTERNAL RC
Alternate pin functions are listed in
Section 1.0 “Device Overview”.
Output depends upon RC or RCIO clock mode.
R
P
R
OSC1/CLKIN
OSC2/CLKOUT
(3)
S (1)
CERAMIC RESONATOR
OPERATION
(XT OR HS MODE)
EXTERNAL RC MODES
F
C
varies with the Oscillator mode
EXT
OSC1/CLKIN
OSC2/CLKOUT
> 20 pF
S
R
PIC
) may be required for
F
(2)
EXT
®
(1)
PIC
MCU
≤ 100 kΩ
®
MCU
To Internal
Logic
Sleep
Internal
Clock
Preliminary
P
)
The RC oscillator frequency is a function of the supply
voltage, the resistor REXT, the capacitor CEXT and the
operating temperature. Other factors affecting the
oscillator frequency are:
• Input threshold voltage variation
• Component tolerances
• Variation in capacitance due to packaging
2.3.4
The External Clock (EC) mode allows an externally
generated logic level clock to be used as the system’s
clock source. When operating in this mode, the
external clock source is connected to the OSC1
allowing OSC2 to be configured as an I/O or as
CLKOUT. The CLKOUT function is selected by the
FOSC bits of the CONFIG1H Configuration register.
When OSC2 is configured as CLKOUT, the frequency
at the pin is the frequency of the EC oscillator divided
by 4.
Three different power settings are available for EC
mode. The power settings allow for a reduced I
device, if the EC clock is known to be in a specific
range. If there is an expected range of frequencies for
the EC clock, select the power mode for the highest
frequency.
2.4
The Secondary External Oscillator is designed to drive
an external 32.768 kHz crystal. This oscillator is
enabled or disabled by the T1OSCEN bit of the T1CON
register. See Section 11.0 “Timer1 Module” for more
information.
EC
EC
EC
Secondary External Oscillator
Low power
Medium power 250 kHz – 4 MHz
High power
EXTERNAL CLOCK
© 2009 Microchip Technology Inc.
0 – 250 kHz
4 – 48 MHz
DD
of the