48GA004 datasheet(97/268 Pages) MICROCHIP

97 / 268 page

 2010 Microchip Technology Inc.

DS39881D-page 97

PIC24FJ64GA004 FAMILY

8.3

Control Registers

The operation of the oscillator is controlled by three

Special Function Registers:

• OSCCON

•CLKDIV

•OSCTUN

The OSCCON register (Register 8-1) is the main con-

trol register for the oscillator. It controls clock source

switching and allows the monitoring of clock sources.

The Clock Divider register (Register 8-2) controls the

features associated with Doze mode, as well as the

postscaler for the FRC oscillator.

The FRC Oscillator Tune register (Register 8-3) allows

the user to fine tune the FRC oscillator over a range of

approximately ±12%. Each bit increment or decrement

changes the factory calibrated frequency of the FRC

oscillator by a fixed amount.

OSCCON: OSCILLATOR CONTROL REGISTER

U-0

R-0

U-0

R/W-x(1)

—

COSC2

COSC1

COSC0

—

NOSC2

NOSC1

NOSC0

bit 15

bit 8

R/SO-0

R/W-0

R-0(3)

U-0R/CO-0U-0

R/W-0

CLKLOCK

IOLOCK(2)

LOCK

—CF

—

SOSCEN

OSWEN

bit 7

bit 0

Legend:

CO = Clear Only bit

SO = Set Only bit

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 15

Unimplemented:

Read as ‘0’

bit 14-12

COSC2:COSC0:

Current Oscillator Selection bits

111

= Fast RC Oscillator with Postscaler (FRCDIV)

110

= Reserved

101

= Low-Power RC Oscillator (LPRC)

100

= Secondary Oscillator (SOSC)

011

= Primary Oscillator with PLL module (XTPLL, HSPLL, ECPLL)

010

= Primary Oscillator (XT, HS, EC)

001

= Fast RC Oscillator with Postscaler and PLL module (FRCPLL)

000

= Fast RC Oscillator (FRC)

bit 11

Unimplemented:

Read as ‘0’

bit 10-8

NOSC2:NOSC0:

New Oscillator Selection bits(1)

111

= Fast RC Oscillator with Postscaler (FRCDIV)

110

= Reserved

101

= Low-Power RC Oscillator (LPRC)

100

= Secondary Oscillator (SOSC)

011

= Primary Oscillator with PLL module (XTPLL, HSPLL, ECPLL)

010

= Primary Oscillator (XT, HS, EC)

001

= Fast RC Oscillator with Postscaler and PLL module (FRCPLL)

000

= Fast RC Oscillator (FRC)

Note 1:

Reset values for these bits are determined by the FNOSC Configuration bits.

The state of the IOLOCK bit can only be changed once an unlocking sequence has been executed. In

addition, if the IOL1WAY Configuration bit is ‘1’ once the IOLOCK bit is set, it cannot be cleared.

Also resets to ‘0’ during any valid clock switch or whenever a non-PLL Clock mode is selected.

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