PIC24HJ32GP302_11 Datasheet, PDF (127/368 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJ32GP302/304, PIC24HJ64GPX02/X04 AND PIC24HJ128GPX02/X04
10.0 POWER-SAVING FEATURES
Note 1: This data sheet summarizes the features
of
the
PIC24HJ32GP302/304,
PIC24HJ64GPX02/X04
and
PIC24HJ128GPX02/X04 families of
devices. It is not intended to be a compre-
hensive reference source. To comple-
ment the information in this data sheet,
refer to Section 9. “Watchdog Timer
and Power Savings Modes” (DS70196)
of the “dsPIC33F/PIC24H Family Refer-
ence Manual”, which is available from the
Microchip website (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.
The PIC24HJ32GP302/304, PIC24HJ64GPX02/X04
and PIC24HJ128GPX02/X04 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.
PIC24HJ32GP302/304,
PIC24HJ64GPX02/X04 and PIC24HJ128GPX02/X04
devices can manage power consumption in four 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
PIC24HJ32GP302/304, PIC24HJ64GPX02/X04 and
PIC24HJ128GPX02/X04 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
PIC24HJ32GP302/304, PIC24HJ64GPX02/X04 and
PIC24HJ128GPX02/X04 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 10-1.
Note:
SLEEP_MODE and IDLE_MODE are con-
stants 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.
10.2.1 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 can 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 wakes 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 10-1: PWRSAV INSTRUCTION SYNTAX
PWRSAV #SLEEP_MODE
PWRSAV #IDLE_MODE
; Put the device into SLEEP mode
; Put the device into IDLE mode
© 2011 Microchip Technology Inc.
DS70293E-page 127