PIC18FXX39 Datasheet, PDF (19/322 Pages) Microchip Technology – Enhanced FLASH Microcontrollers with Single Phase Induction Motor Control Kernel

2.0 OSCILLATOR
CONFIGURATIONS
2.1 Oscillator Types
The PIC18FXX39 can be operated in four different
Oscillator modes at a frequency of 20 MHz. The user
can program three configuration bits (FOSC2, FOSC1,
and FOSC0) to select one of these four modes:
1. HS
2. HS + PLL
3. EC
4. ECIO
High Speed Crystal/Resonator
High Speed Crystal/Resonator
with PLL enabled using 5 MHz
crystal
External Clock
External Clock with I/O pin
enabled
Note:
The operation of the Motor Control kernel
and its APIs (Section 14.0) is based on an
assumed clock frequency of 20 MHz.
Changing the oscillator frequency will
change the timing used in the Motor Con-
trol kernel accordingly. To achieve the best
results in motor control applications, a
clock frequency of 20 MHz is highly
recommended.
2.2 Crystal Oscillator/Ceramic
Resonators
In HS or HS+PLL Oscillator modes, a crystal or ceramic
resonator is connected to the OSC1 and OSC2 pins to
establish oscillation. Figure 2-1 shows the pin
connections.
The PIC18FXX39 oscillator design requires the use of
a parallel cut crystal.
Note:
Use of a series cut crystal may give a fre-
quency out of the crystal manufacturers
specifications.
PIC18FXX39
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
RF⁽³⁾
To
Internal
Logic
RS⁽²⁾
C2⁽¹⁾
OSC2
SLEEP
PIC18FXX39
Note 1: See Table 2-1 for recommended values of
C1 and C2.
2: A series resistor (RS) may be required for
AT strip cut crystals.
3: RF varies with the Oscillator mode chosen.
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:
EXTERNAL CLOCK INPUT
OPERATION (HS OSC
CONFIGURATION)
Clock from
Ext. System
Open
OSC1
PIC18FXX39
OSC2
Note 1: Higher capacitance increases the stability
of the oscillator, but also increases the
start-up time.
2: Since each resonator/crystal has its own
characteristics, the user should consult the
resonator/crystal manufacturer for appro-
priate values of external components, or
verify oscillator performance.
 2002-2013 Microchip Technology Inc.
Preliminary
DS30485B-page 19