PIC24FJ16GA MICROCHIP [Microchip Technology], PIC24FJ16GA Datasheet - Page 94

• Manufacturer Part Number: PIC24FJ16GA
• Description: 28/44-Pin General Purpose, 16-Bit Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

PIC24FJ64GA004 FAMILY
REGISTER 7-3:
7.4
With few limitations, applications are free to switch
between any of the four clock sources (POSC, SOSC,
FRC and LPRC) under software control and at any
time. To limit the possible side effects that could result
from this flexibility, PIC24F devices have a safeguard
lock built into the switching process.
DS39881C-page 92
bit 15
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 15-6
bit 5-0
Note 1:
Note:
U-0
U-0
—
—
Clock Switching Operation
Increments or decrements of TUN5:TUN0 may not change the FRC frequency in equal steps over the
FRC tuning range, and may not be monotonic.
The primary oscillator mode has three
different submodes (XT, HS and EC)
which are determined by the POSCMDx
Configuration bits. While an application
can switch to and from primary oscillator
mode in software, it cannot switch
between the different primary submodes
without reprogramming the device.
Unimplemented: Read as ‘0’
TUN5:TUN0: FRC Oscillator Tuning bits
011111 = Maximum frequency deviation
011110 =
•
•
•
000001 =
000000 = Center frequency, oscillator is running at factory calibrated frequency
111111 =
•
•
•
100001 =
100000 = Minimum frequency deviation
U-0
U-0
—
—
OSCTUN: FRC Oscillator Tune Register
W = Writable bit
‘1’ = Bit is set
TUN5
R/W-0
U-0
—
(1)
TUN4
R/W-0
U-0
—
Preliminary
(1)
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
TUN3
R/W-0
7.4.1
To enable clock switching, the FCKSM1 Configuration
bit in Flash Configuration Word 2 must be programmed
to ‘0’. (Refer to Section 23.1 “Configuration Bits” for
further details.) If the FCKSM1 Configuration bit is
unprogrammed (‘1’), the clock switching function and
Fail-Safe Clock Monitor function are disabled. This is
the default setting.
The NOSCx control bits (OSCCON<10:8>) do not
control the clock selection when clock switching is dis-
abled. However, the COSCx bits (OSCCON<14:12>)
will reflect the clock source selected by the FNOSCx
Configuration bits.
The OSWEN control bit (OSCCON<0>) has no effect
when clock switching is disabled. It is held at ‘0’ at all
times.
U-0
—
(1)
ENABLING CLOCK SWITCHING
TUN2
R/W-0
U-0
—
(1)
© 2008 Microchip Technology Inc.
x = Bit is unknown
TUN1
R/W-0
U-0
—
(1)
TUN0
R/W-0
U-0
—
(1)
bit 8
bit 0