Datasheet

© 2009 Microchip Technology Inc. DS70286C-page 147
dsPIC33FJXXXGPX06/X08/X10
10.0 POWER-SAVING FEATURES
The dsPIC33FJXXXGPX06/X08/X10 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. dsPIC33FJXXXGPX06/X08/X10
devices can manage power consumption in four
different 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
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
dsPIC33FJXXXGPX06/X08/X10 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
NOSC 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
dsPIC33FJXXXGPX06/X08/X10 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 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 has these features:
• 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
during Sleep mode 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 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 is disabled in Sleep mode.
The device will wake-up from Sleep mode on any of
these events:
• Any interrupt source that is individually enabled.
• Any form of device Reset.
• A WDT time-out.
On wake-up from Sleep, the processor restarts 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 the dsPIC33FJXXXGPX06/X08/X10
family of devices. However, it is not
intended to be a comprehensive reference
source. To complement the information in
this data sheet, refer to Section 9.
“Watchdog Timer and Power-Saving
Modes” (DS70196) in the “dsPIC33F
Family Reference Manual”, which is avail-
able from the Microchip web site
(www.microchip.com).
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