PIC24EP256GU810-I Datasheet, PDF (191/622 Pages) Electronic Film Capacitors, Inc. – 16-Bit Microcontrollers and Digital Signal Controllers with High-Speed PWM, USB and Advanced Analog

dsPIC33EPXXX(GP/MC/MU)806/810/814 and PIC24EPXXX(GP/GU)810/814
10.0 POWER-SAVING FEATURES
Note 1: This data sheet summarizes the features
of the dsPIC33EPXXX(GP/MC/MU)806/
810/814 and PIC24EPXXX(GP/GU)810/
814 families of devices. It is not intended
to be a comprehensive reference source.
To complement the information in this
data sheet, refer to Section 9. “Watch-
dog Timer and Power-Saving Modes”
(DS70615) of the “dsPIC33E/PIC24E
Family Reference Manual”, which is
available from the Microchip web site
(www.microchip.com).
2: Some registers and associated bits
described in this section may not be
available on all devices. Refer to
Section 4.0 “Memory Organization” in
this data sheet for device-specific register
and bit information.
The dsPIC33EPXXX(GP/MC/MU)806/810/814 and
PIC24EPXXX(GP/GU)810/814 devices provide the
ability to manage power consumption by selectively
managing clocking to the CPU and the peripherals.
In general, a lower clock frequency and a reduction
in the number of circuits being clocked constitutes
lower consumed power.
dsPIC33EPXXX(GP/MC/MU)806/810/814
and
PIC24EPXXX(GP/GU)810/814 devices can
manage power consumption in four ways:
• Clock frequency
• Instruction-based Sleep and Idle modes
• Software-controlled Doze mode
• Selective peripheral control in software
Combinations of these methods can be used to selec-
tively tailor an application’s power consumption while
still maintaining critical application features, such as
timing-sensitive communications.
10.1 Clock Frequency and Clock
Switching
The dsPIC33EPXXX(GP/MC/MU)806/810/814 and
PIC24EPXXX(GP/GU)810/814 devices allow a wide
range of clock frequencies to be selected under
application control. If the system clock configuration is
not locked, users can choose low-power or high-
precision oscillators by simply changing the NOSCx
bits (OSCCON<10:8>). The process of changing a
system clock during operation, as well as limitations to
the process, are discussed in more detail in
Section 9.0 “Oscillator Configuration”.
10.2 Instruction-Based Power-Saving
Modes
The dsPIC33EPXXX(GP/MC/MU)806/810/814 and
PIC24EPXXX(GP/GU)810/814 devices have two
special power-saving modes that are entered
through the execution of a special PWRSAV
instruction. Sleep mode stops clock operation and
halts all code execution. Idle mode halts the CPU
and code execution, but allows peripheral modules
to continue operation. The assembler syntax of the
PWRSAV instruction is shown in Example 10-1.
Note:
SLEEP_MODE and IDLE_MODE are con-
stants defined in the assembler include
file for the selected device.
Sleep and Idle modes can be exited as a result of an
enabled interrupt, WDT time-out or a device Reset. When
the device exits these modes, it is said to wake up.
10.2.1 SLEEP MODE
The following occur in Sleep mode:
• The system clock source is shut down. If an
on-chip oscillator is used, it is turned off.
• The device current consumption is reduced to a
minimum, provided that no I/O pin is sourcing
current.
• The Fail-Safe Clock Monitor does not operate,
since the system clock source is disabled.
• The LPRC clock continues to run in Sleep mode if
the WDT is enabled.
• The WDT, if enabled, is automatically cleared
prior to entering Sleep mode.
• Some device features or peripherals can continue
to operate. This includes items such as the input
change notification on the I/O ports, or peripherals
that use an external clock input.
• Any peripheral that requires the system clock
source for its operation is disabled.
The device wakes up from Sleep mode on any of the
these events:
• Any interrupt source that is individually enabled
• Any form of device Reset
• A WDT time-out
On wake-up from Sleep mode, the processor restarts
with the same clock source that was active when Sleep
mode was entered.
EXAMPLE 10-1: PWRSAV INSTRUCTION SYNTAX
PWRSAV #SLEEP_MODE
PWRSAV #IDLE_MODE
; Put the device into SLEEP mode
; Put the device into IDLE mode
 2009-2012 Microchip Technology Inc.
DS70616G-page 191