PIC24HJ128GP206-I Datasheet, PDF (129/286 Pages) Microchip Technology – High-Performance, 16-Bit Microcontrollers

PIC24HJXXXGPX06/X08/X10
9.0 POWER-SAVING FEATURES
Note:
This data sheet summarizes the features
of
this
group
of PIC24HJXXXGPX06/X08/X10 devices.
It is not intended to be a comprehensive
reference source. To complement the
information in this data sheet, refer to the
“PIC24H Family Reference Manual”.
Refer to the Microchip web site
(www.microchip.com) for the latest
PIC24H Family Reference Manual
sections.
The PIC24HJXXXGPX06/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 con-
sumed power. PIC24HJXXXGPX06/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 selec-
tively tailor an application’s power consumption while
still maintaining critical application features, such as
timing-sensitive communications.
9.1 Clock Frequency and Clock
Switching
PIC24HJXXXGPX06/X08/X10 devices allow a wide
range of clock frequencies to be selected under appli-
cation control. If the system clock configuration is not
locked, users can choose low-power or high-precision
oscillators by simply changing the NOSC bits (OSC-
CON<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 8.0 “Oscillator
Configuration”.
9.2 Instruction-Based Power-Saving
Modes
PIC24HJXXXGPX06/X08/X10 devices have two spe-
cial 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 assem-
bly syntax of the
PWRSAV instruction is shown in Example 9-1.
Note:
SLEEP_MODE and IDLE_MODE are
constants 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”.
9.2.1 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 the
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 9-1: PWRSAV INSTRUCTION SYNTAX
PWRSAV #SLEEP_MODE
PWRSAV #IDLE_MODE
; Put the device into SLEEP mode
; Put the device into IDLE mode
© 2007 Microchip Technology Inc.
DS70175F-page 127