PIC24FJ256GB108-I Datasheet, PDF (123/352 Pages) Microchip Technology – 64/80/100-Pin, 16-Bit Flash Microcontrollers with USB On-The-Go (OTG)

PIC24FJ256GB110 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 CLKDIV register (Register 8-2) controls the
features associated with Doze mode, as well as the
postscaler for the FRC Oscillator. The OSCTUN
register (Register 8-3) allows the user to fine tune the
FRC Oscillator over a range of approximately ±12%.
REGISTER 8-1: OSCCON: OSCILLATOR CONTROL REGISTER
U-0
R-0
R-0
R-0
U-0
R/W-x⁽¹⁾
—
COSC2
COSC1
COSC0
—
NOSC2
bit 15
R/W-x⁽¹⁾
NOSC1
R/W-x⁽¹⁾
NOSC0
bit 8
R/SO-0
CLKLOCK
bit 7
R/W-0
IOLOCK⁽²⁾
R-0⁽³⁾
LOCK
U-0
R/CO-0
R/W-0
R/W-0
R/W-0
—
CF
POSCEN SOSCEN
OSWEN
bit 0
Legend:
R = Readable bit
-n = Value at POR
CO = Clear Only bit
W = Writable bit
‘1’ = Bit is set
SO = Set Only bit
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 15
bit 14-12
bit 11
bit 10-8
Unimplemented: Read as ‘0’
COSC<2:0>: 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)
Unimplemented: Read as ‘0’
NOSC<2:0>: 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:
2:
3:
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.
 2009 Microchip Technology Inc.
DS39897C-page 123