Datasheet

 2009-2012 Microchip Technology Inc. DS70592D-page 133
PIC24HJXXXGPX06A/X08A/X10A
10.0 POWER-SAVING FEATURES
The PIC24HJXXXGPX06A/X08A/X10A 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.
PIC24HJXXXGPX06A/X08A/X10A 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 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
PIC24HJXXXGPX06A/X08A/X10A 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-preci-
sion 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 pro-
cess, are discussed in more detail in Section 9.0
“Oscillator Configuration”.
10.2 Instruction-Based Power-Saving
Modes
PIC24HJXXXGPX06A/X08A/X10A 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 execu-
tion. 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 1: This data sheet summarizes the features
of the PIC24HJXXXGPX06A/X08A/X10A
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) of
the “dsPIC33F/PIC24H 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.
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