Datasheet

 2011-2017 Microchip Technology Inc. DS30009995E-page 125
PIC24FV32KA304 FAMILY
10.0 POWER-SAVING FEATURES
The PIC24FV32KA304 family of devices provides 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. All PIC24F devices manage power
consumption in four different ways:
• Clock Frequency
• Instruction-Based Sleep, Idle and Deep Sleep
modes
• Software Controlled Doze mode
• Selective Peripheral Control in Software
Combinations of these methods can be used to
selectively tailor an application’s power consumption,
while still maintaining critical application features, such
as timing-sensitive communications.
10.1 Clock Frequency and Clock
Switching
PIC24F devices allow for 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. 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
PIC24F 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. Deep Sleep mode stops clock
operation, code execution and all peripherals, except
RTCC and DSWDT. It also freezes I/O states and
removes power to SRAM and Flash memory.
The assembly syntax of the PWRSAV instruction is
shown in Example 10-1.
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
Sleep mode includes these features:
• The system clock source is shut down. If an
on-chip oscillator is used, it is turned off.
• The device current consumption will be reduced
to a minimum provided that no I/O pin is sourcing
current.
• The I/O pin directions and states are frozen.
• The Fail-Safe Clock Monitor does not operate
during Sleep mode since the system clock source
is disabled.
• The LPRC clock will continue to run in Sleep
mode if the WDT or RTCC with LPRC as the clock
source is enabled.
• The WDT, if enabled, is automatically cleared
prior to entering Sleep mode.
• Some device features or peripherals may
continue to operate in Sleep mode. 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 will be
disabled in Sleep mode.
The device will wake-up from Sleep mode on any of
these events:
• On any interrupt source that is individually
enabled
• On any form of device Reset
• On a WDT time-out
On wake-up from Sleep, the processor will restart with
the same clock source that was active when Sleep
mode was entered.
EXAMPLE 10-1: PWRSAV INSTRUCTION SYNTAX
Note: This data sheet summarizes the features
of this group of PIC24F devices. It is not
intended to be a comprehensive refer-
ence source. For more information, refer
to the “dsPIC33/PIC24 Family Reference
Manual”, ”Power-Saving Features with
Deep Sleep” (DS39727).
Note: SLEEP_MODE and IDLE_MODE are
constants defined in the assembler
include file for the selected device.
PWRSAV #SLEEP_MODE ; Put the device into SLEEP mode
PWRSAV #IDLE_MODE ; Put the device into IDLE mode
BSET DSCON, #DSEN ; Enable Deep Sleep
PWRSAV #SLEEP_MODE ; Put the device into Deep SLEEP mode