Microchip Technology dsPIC30F - 11 = Primary Oscillator

© 2004 Microchip Technology Inc. DS70054C-page 7-7
Section 7. Oscillator
Oscillator
7
Register 7-1: OSCCON: Oscillator Control Register
Upper Byte:
R/W-0 R/W-0 R-y R-y U-0 U-0 R/W-y R/W-y
TUN3 TUN2 COSC<1:0> TUN1 TUN0 NOSC<1:0>
bit 15 bit 8
Lower Byte:
R/W-0 R/W-0 R-0 U-0 R/W-0 U-0 R/W-0 R/W-0
POST<1:0> LOCK — CF — LPOSCEN OSWEN
bit 7 bit 0
bit 15-14 TUN<3:2>: Upper 2 bits of the TUN bit-field. Refer to the description of TUN<1:0> (OSCCON<11:10>)
bits for details.
bit 13-12 COSC<1:0>: Current Oscillator Source Status bits
11 = Primary oscillator
10 = Internal LPRC oscillator
01 = Internal FRC oscillator
00 = Low Power 32 kHz Crystal oscillator (Timer1)
bit 11-10 TUN<1:0>: Lower 2 bits of the TUN bit-field.
The four bit field specified by TUN<3:0> allows the user to tune the internal fast RC oscillator which has
a nominal frequency of 8 MHz. The user may be able to tune the frequency of the FRC oscillator within
a range of +/- 12% (or 960 kHz) in steps of 1.5% around the factory-calibrated frequency setting, as
follows:
TUN<3:0> = 0111 provides the highest frequency
......
TUN<3:0> = 0000 provides the factory-calibrated frequency
......
TUN<3:0> = 1000 provides the lowest frequency
Note: Refer to the device-specific data sheet for the tuning range and tuning step size for the FRC
oscillator on your device.
bit 9-8 NOSC<1:0>: New Oscillator Group Selection bits
11 = Primary oscillator
10 = Internal LPRC oscillator
01 = Internal FRC oscillator
00 = Low Power 32 kHz Crystal oscillator (Timer1)
bit 7-6 POST<1:0>: Oscillator Postscaler Selection bits
11 = Oscillator postscaler divides clock by 64
10 = Oscillator postscaler divides clock by 16
01 = Oscillator postscaler divides clock by 4
00 = Oscillator postscaler does not alter clock
bit 5 LOCK: PLL Lock Status bit
1 = Indicates that PLL is in lock
0 = Indicates that PLL is out of lock (or disabled)
bit 4 Unimplemented: Read as ‘0’
bit 3 CF: Clock Fail Status bit
1 = FSCM has detected a clock failure
0 = FSCM has not detected a clock failure
bit 2 Unimplemented: Read as ‘0’