Microchip Technology MA180025 データシート

 2010 Microchip Technology Inc.

DS39933D-page 35

The PIC18F87J90 family of devices can be operated in
eight different oscillator modes:
1.

ECPLL

OSC1/OSC2 as primary; ECPLL
oscillator with PLL enabled, CLKO on
RA6

2.

EC

OSC1/OSC2 as primary; external
clock with F

OSC

/4 output

3.

HSPLL

OSC1/OSC2 as primary; high-speed
crystal/resonator with software PLL
control

4.

HS

OSC1/OSC2 as primary; high-speed
crystal/resonator

5.

INTPLL1 Internal oscillator block with software

PLL control, F

OSC

/4 output on RA6

and I/O on RA7

6.

INTIO1

Internal oscillator block with F

OSC

/4

output on RA6 and I/O on RA7

7.

INTPLL2 Internal oscillator block with software

PLL control and I/O on RA6 and RA7

8.

INTIO2

Internal oscillator block with I/O on
RA6 and RA7

All of these modes are selected by the user by
programming the FOSC<2:0> Configuration bits.
In addition, PIC18F87J90 family devices can switch
between different clock sources, either under software
control or automatically under certain conditions. This
allows for additional power savings by managing
device clock speed in real time without resetting the
application.
The clock sources for the PIC18F87J90 family of
devices are shown in Figure 3-1. 

4 x PLL

FOSC<2:0> 

T1OSCEN

Enable

Oscillator

T1OSO

T1OSI

Clock Source Option 
for Other Modules

OSC1

OSC2

Sleep

HSPLL, ECPLL, INTPLL

HS, EC

T1OSC

CPU

Peripherals

IDLEN

P

o

st

sc

aler

MU

X

MU

X

8 MHz
4 MHz

2 MHz
1 MHz

500 kHz

125 kHz

250 kHz

OSCCON<6:4>

111

110

101

100

011

010

001

000

31 kHz

INTRC

Source

WDT, PWRT, FSCM

8 MHz

Internal Oscillator

(INTOSC)

OSCCON<6:4>

Clock

Control

OSCCON<1:0>

 

Source

8 MHz

31 kHz (INTRC)

0

1

OSCTUNE<7>

and Two-Speed Start-up

OSCTUNE<6>