PIC24FV32KA304-I/PT Microchip Technology, PIC24FV32KA304-I/PT Datasheet - Page 123

• Manufacturer Part Number: PIC24FV32KA304-I/PT
• Description: MCU 32KB FLASH 2KB RAM 44-TQFP
• Manufacturer: Microchip Technology

Specifications of PIC24FV32KA304-I/PT

• Processor Series: PIC24FV
• Core: PIC
• Data Bus Width: 16 bit
• Program Memory Type: Flash
• Program Memory Size: 32 KB
• Data Ram Size: 2 KB
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TQFP-44
• Development Tools By Supplier: MPLAB IDE Software
• Minimum Operating Temperature: - 40 C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

9.4
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.
9.4.1
To enable clock switching, the FCKSM1 Configuration bit
in the FOSC Configuration register must be programmed
to ‘0’. (Refer to
further details.) If the FCKSM1 Configuration bit is
unprogrammed (‘1’), the clock switching function and
FSCM 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
disabled. 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.
9.4.2
At a minimum, performing a clock switch requires this
basic sequence:
1.
2.
3.
4.
5.
 2011 Microchip Technology Inc.
Note:
If
(OSCCON<14:12>), to determine the current
oscillator source.
Perform the unlock sequence to allow a write to
the OSCCON register high byte.
Write the appropriate value to the NOSCx bits
(OSCCON<10:8>) for the new oscillator source.
Perform the unlock sequence to allow a write to
the OSCCON register low byte.
Set the OSWEN bit to initiate the oscillator
switch.
Clock Switching Operation
desired,
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.
ENABLING CLOCK SWITCHING
OSCILLATOR SWITCHING
SEQUENCE
Section 26.0 “Special Features”
read
the
COSCx
bits
PIC24FV32KA304 FAMILY
for
Once the basic sequence is completed, the system
clock hardware responds automatically, as follows:
1.
2.
3.
4.
5.
6.
Note 1: The processor will continue to execute
The clock switching hardware compares the
COSCx bits with the new value of the NOSCx
bits. If they are the same, then the clock switch
is a redundant operation. In this case, the
OSWEN bit is cleared automatically and the
clock switch is aborted.
If a valid clock switch has been initiated, the
LOCK (OSCCON<5>) and CF (OSCCON<3>)
bits are cleared.
The new oscillator is turned on by the hardware
if it is not currently running. If a crystal oscillator
must be turned on, the hardware will wait until
the OST expires. If the new source is using the
PLL, then the hardware waits until a PLL lock is
detected (LOCK = 1).
The hardware waits for 10 clock cycles from the
new clock source and then performs the clock
switch.
The hardware clears the OSWEN bit to indicate a
successful clock transition. In addition, the
NOSCx bits value is transferred to the COSCx
bits.
The old clock source is turned off at this time,
with the exception of LPRC (if WDT, FSCM or
RTCC with LPRC as clock source are enabled)
or SOSC (if SOSCEN remains enabled).
2: Direct clock switches between any
code throughout the clock switching
sequence. Timing-sensitive code should
not be executed during this time.
Primary Oscillator mode with PLL and
FRCPLL mode are not permitted. This
applies to clock switches in either
direction.
application must switch to FRC mode as
a transition clock source between the two
PLL modes.
In
these
DS39995B-page 123
instances,
the