PIC24F04KA201 datasheet(93/224 Pages) MICROCHIP

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Preliminary

DS39937B-page 91

PIC24F04KA201 FAMILY

9.0

POWER-SAVING FEATURES

The PIC24F04KA201 family of devices provides 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. All PIC24F devices manage power

consumption in four different ways:

• Clock frequency

• Instruction-based Sleep, Idle and Deep Sleep

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.

9.1

Clock Frequency and Clock

Switching

PIC24F devices allow for 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. 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

PIC24F 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. Deep Sleep mode stops clock

operation, code execution and all peripherals except

DSWDT. It also freezes I/O states and removes power

to SRAM and Flash memory.

The assembly syntax of the PWRSAV instruction is

shown in Example 9-1.

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”.

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 will be reduced

to a minimum provided that no I/O pin is sourcing

current.

• The I/O pin directions and states are frozen.

• The Fail-Safe Clock Monitor does not operate

during Sleep mode since the system clock source

is disabled.

• The LPRC clock will continue to run in Sleep

mode if the WDT with LPRC as a clock source 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 will be disabled in

Sleep mode.

The device will wake-up from Sleep mode on any of

these events:

• On any interrupt source that is individually

enabled

• On any form of device Reset

• On a WDT time-out

On wake-up from Sleep, the processor will restart with

the same clock source that was active when Sleep

mode was entered.

EXAMPLE 9-1:

PWRSAV INSTRUCTION SYNTAX

Note:

This data sheet summarizes the features

of this group of PIC24F devices. It is not

intended to be a comprehensive reference

source. For more information, refer to the

“PIC24F

Family

Reference

Manual”

Section 39. “Power-Saving Features

with Deep Sleep”

(DS39727).

Note:

SLEEP_MODE

and IDLE_MODE are con-

stants 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

BSET

DSCON, #DSEN

; Enable Deep Sleep

PWRSAV

#SLEEP_MODE

; Put the device into Deep SLEEP mode

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