PIC18F-LF1XK50 Datasheet, PDF (17/420 Pages) Microchip Technology – 20-Pin USB Flash Microcontrollers

2.3.1
PRIMARY EXTERNAL OSCILLATOR
SHUT-DOWN
The Primary External Oscillator can be enabled or dis-
abled via software. To enable software control of the
Primary External Oscillator, the PCLKEN bit of the
CONFIG1H Configuration register must be set. With
the PCLKEN bit set, the Primary External Oscillator is
controlled by the PRI_SD bit of the OSCCON2 register.
The Primary External Oscillator will be enabled when
the PRI_SD bit is set, and disabled when the PRI_SD
bit is clear.
Note:
The Primary External Oscillator cannot be
shut down when it is selected as the
System Clock. To shut down the oscillator,
the system clock source must be either
the Secondary Oscillator or the Internal
Oscillator.
2.3.2
LP, XT AND HS OSCILLATOR
MODES
The LP, XT and HS modes support the use of quartz
crystal resonators or ceramic resonators connected to
OSC1 and OSC2 (Figure 2-2). The mode selects a low,
medium or high gain setting of the internal inverter-
amplifier to support various resonator types and speed.
LP Oscillator mode selects the lowest gain setting of the
internal inverter-amplifier. LP mode current consumption
is the least of the three modes. This mode is best suited
to drive resonators with a low drive level specification, for
example, tuning fork type crystals.
XT Oscillator mode selects the intermediate gain
setting of the internal inverter-amplifier. XT mode
current consumption is the medium of the three modes.
This mode is best suited to drive resonators with a
medium drive level specification.
HS Oscillator mode selects the highest gain setting of the
internal inverter-amplifier. HS mode current consumption
is the highest of the three modes. This mode is best
suited for resonators that require a high drive setting.
Figure 2-2 and Figure 2-3 show typical circuits for
quartz crystal and ceramic resonators, respectively.
PIC18F/LF1XK50
FIGURE 2-2:
QUARTZ CRYSTAL
OPERATION (LP, XT OR
HS MODE)
PIC^® MCU
C1
Quartz
Crystal
OSC1/CLKIN
RF⁽²⁾
To Internal
Logic
Sleep
C2
RS⁽¹⁾
OSC2/CLKOUT
Note 1: A series resistor (RS) may be required for
quartz crystals with low drive level.
2: The value of RF varies with the Oscillator mode
selected (typically between 2 M to 10 M.
Note 1: Quartz crystal characteristics vary
according to type, package and
manufacturer. The user should consult the
manufacturer data sheets for specifications
and recommended application.
2: Always verify oscillator performance over
the VDD and temperature range that is
expected for the application.
3: For oscillator design assistance, reference
the following Microchip Applications Notes:
• AN826, “Crystal Oscillator Basics and
Crystal Selection for rfPIC^® and PIC^®
Devices” (DS00826)
• AN849, “Basic PIC^® Oscillator Design”
(DS00849)
• AN943, “Practical PIC^® Oscillator
Analysis and Design” (DS00943)
• AN949, “Making Your Oscillator Work”
(DS00949)
 2010 Microchip Technology Inc.
Preliminary
DS41350E-page 17