Microchip Technology ARD00385 Data Sheet
2009-2011 Microchip Technology Inc.
DS39957D-page 41
PIC18F87K90 FAMILY
3.0
OSCILLATOR
CONFIGURATIONS
CONFIGURATIONS
3.1
Oscillator Types
The PIC18F87K90 family of devices can be operated in
the following oscillator modes:
• EC
the following oscillator modes:
• EC
External Clock, RA6 available
• ECIO
External Clock, Clock Out RA6
(F
(F
OSC
/4 on RA6)
• HS
High-Speed Crystal/Resonator
• XT
Crystal/Resonator
• LP
Low-Power Crystal
• RC
External Resistor/Capacitor, RA6
available
available
• RCIO
External Resistor/Capacitor, Clock
Out RA6 (F
Out RA6 (F
OSC
/4 on RA6)
• INTIO2
Internal Oscillator with I/O on RA6
and RA7
and RA7
• INTIO1
Internal Oscillator with F
OSC
/4 Output
on RA6 and I/O on RA7
There is also an option for running the 4xPLL on any of
the clock sources in the input frequency range of 4 to
16 MHz.
The PLL is enabled by setting the PLLCFG bit
(CONFIG1H<4>) or the PLLEN bit (OSCTUNE<6>).
For the EC and HS mode, the PLLEN (software) or
PLLCFG (CONFIG) bit can be used to enable the PLL.
For the INTIOx modes (HF-INTOSC):
• Only the PLLEN can enable the PLL (PLLCFG is
the clock sources in the input frequency range of 4 to
16 MHz.
The PLL is enabled by setting the PLLCFG bit
(CONFIG1H<4>) or the PLLEN bit (OSCTUNE<6>).
For the EC and HS mode, the PLLEN (software) or
PLLCFG (CONFIG) bit can be used to enable the PLL.
For the INTIOx modes (HF-INTOSC):
• Only the PLLEN can enable the PLL (PLLCFG is
ignored).
• When the oscillator is configured for the internal
oscillator (OSC<3:0> = 100x), the PLL can be
enabled only when the HF-INTOSC frequency is
8 or 16 MHz.
enabled only when the HF-INTOSC frequency is
8 or 16 MHz.
When the RA6 and RA7 pins are not used for an oscil-
lator function or CLKOUT function, they are available
as general purpose I/Os.
lator function or CLKOUT function, they are available
as general purpose I/Os.
To optimize power consumption when using EC/HS/
XT/LP/RC as the primary oscillator, the frequency input
range can be configured to yield an optimized power
bias:
• Low-Power Bias – External frequency less than
XT/LP/RC as the primary oscillator, the frequency input
range can be configured to yield an optimized power
bias:
• Low-Power Bias – External frequency less than
160 kHz
• Medium Power Bias – External frequency
between 160 kHz and 16 MHz
• High-Power Bias – External frequency greater
than 16 MHz
All of these modes are selected by the user by
programming the OSC<3:0> Configuration bits
(CONFIG1H<3:0>). In addition, PIC18F87K90 family
devices can switch between different clock sources,
either under software control or under certain condi-
tions, automatically. This allows for additional power
savings by managing device clock speed in real time
without resetting the application. The clock sources for
the PIC18F87K90 family of devices are shown in
programming the OSC<3:0> Configuration bits
(CONFIG1H<3:0>). In addition, PIC18F87K90 family
devices can switch between different clock sources,
either under software control or under certain condi-
tions, automatically. This allows for additional power
savings by managing device clock speed in real time
without resetting the application. The clock sources for
the PIC18F87K90 family of devices are shown in
For the HS and EC mode, there are additional power
modes of operation – depending on the frequency of
operation.
HS1 is the Medium Power mode with a frequency
range of 4 MHz to 16 MHz. HS2 is the High-Power
mode where the oscillator frequency can go from
16 MHz to 25 MHz. HS1 and HS2 are achieved by
setting the CONFIG1H<3:0> correctly. (For details, see
modes of operation – depending on the frequency of
operation.
HS1 is the Medium Power mode with a frequency
range of 4 MHz to 16 MHz. HS2 is the High-Power
mode where the oscillator frequency can go from
16 MHz to 25 MHz. HS1 and HS2 are achieved by
setting the CONFIG1H<3:0> correctly. (For details, see
on page
.)
EC mode has these modes of operation:
• EC1 – For low power with a frequency range up to
• EC1 – For low power with a frequency range up to
160 kHz
• EC2 – Medium power with a frequency range of
160 kHz to 16 MHz
• EC3 – High power with a frequency range of
16 MHz to 64 MHz
EC1, EC2 and EC3 are achieved by setting the
CONFIG1H<3:0> correctly. (For details, see
CONFIG1H<3:0> correctly. (For details, see
on page
.)
shows the HS and EC modes’ frequency
range and OSC<3:0> settings.