PIC24FJ16MC101_12 Datasheet, PDF (109/350 Pages) Microchip Technology – 16-bit Microcontrollers (up to 32 KB Flash and 2 KB SRAM)

PIC24FJ16MC101/102 AND PIC24FJ32MC101/102/104
9.0 POWER-SAVING FEATURES
Note 1: This data sheet summarizes the features
of the PIC24FJ16MC101/102 and
PIC24FJ32MC101/102/104 family of
devices. It is not intended to be a
comprehensive reference source. To
complement the information in this data
sheet, refer to Section 9. “Watchdog
Timer (WDT)” (DS39697) and Section
10. “Power-Saving Features”
(DS39698) in the “PIC24F Family
Reference Manual”, which are available
from the Microchip web site
(www.microchip.com).
2: It is important to note that the
specifications in Section 26.0 “Electri-
cal Characteristics” of this data sheet,
supercede any specifications that may be
provided in PIC24F Family Reference
Manual sections.
3: 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 PIC24FJ16MC101/102 and PIC24FJ32MC101/
102/104 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.
PIC24FJ16MC101/102 and PIC24FJ32MC101/102/
104 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
PIC24FJ16MC101/102 and PIC24FJ32MC101/102/
104 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 8.0 “Oscillator
Configuration”.
9.2 Instruction-Based Power-Saving
Modes
PIC24FJ16MC101/102 and PIC24FJ32MC101/102/104
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 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
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 may 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 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 mode, 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
© 2011-2012 Microchip Technology Inc.
Preliminary
DS39997C-page 109