Datasheet

 2010 Microchip Technology Inc. DS39975A-page 139
PIC24FJ256GB210 FAMILY
8.3 Control Registers
The following four Special Function Registers control
the operation of the oscillator:
• OSCCON
•CLKDIV
•OSCTUN
• REFOCON
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 ±1.5%.
The REFOCON register (Register 8-5) controls the
frequency of the reference clock out.
REGISTER 8-1: OSCCON: OSCILLATOR CONTROL REGISTER
U-0 R-x, HSC
(1)
R-x, HSC
(1)
R-x, HSC
(1)
U-0 R/W-x
(1)
R/W-x
(1)
R/W-x
(1)
— COSC2 COSC1 COSC0 — NOSC2 NOSC1 NOSC0
bit 15 bit 8
R/S-0 R/W-0 R-0, HSC
(3)
U-0 R/C-0, HS R/W-0 R/W-0 R/W-0
CLKLOCK IOLOCK
(2)
LOCK — CF POSCEN SOSCEN OSWEN
bit 7 bit 0
Legend: C = Clearable bit S = Settable bit HSC = Hardware Settable/Clearable 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
HS = Hardware Settable bit
bit 15 Unimplemented: Read as ‘0’
bit 14-12 COSC<2:0>: Current Oscillator Selection bits
(1)
111 = Fast RC Oscillator with Postscaler (FRCDIV)
110 = Fast RC/16 Oscillator
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 NOSC<2:0>: New Oscillator Selection bits
(1)
111 = Fast RC Oscillator with Postscaler (FRCDIV)
110 = Fast RC/16 Oscillator
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.
2: 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.
3: Also resets to ‘0’ during any valid clock switch or whenever a non PLL Clock mode is selected.