Active And Idle Modes; Pm1; Pm2; Pm3 - Texas Instruments CC253x User Manual

Power Management Introduction

4.1.1 Active and Idle Modes

Active mode is the fully functional mode of operation where the CPU, peripherals, and RF transceiver are
active. The digital voltage regulator is turned on.
Active mode is used for normal operation. By enabling the PCON.IDLE bit while in active mode
(SLEEPCMD.MODE = 0x00), the CPU core stops operating and the idle mode is entered. All other
peripherals function normally, and any enabled interrupt wakes up the CPU core (to transition back from
idle mode to active mode).

4.1.2 PM1

In PM1, the high-frequency oscillators are powered down (32-MHz XOSC and 16-MHz RCOSC). The
voltage regulator and the enabled 32-kHz oscillator are on. When PM1 is entered, a power-down
sequence is run.
PM1 is used when the expected time until a wakeup event is relatively short (less than 3 ms), because
PM1 uses a fast power-down and power-up sequence.

4.1.3 PM2

PM2 has the second-lowest power consumption. In PM2, the power-on reset, external interrupts, selected
32-kHz oscillator, and Sleep Timer peripherals are active. I/O pins retain the I/O mode and output value
set before entering PM2. All other internal circuits are powered down. The voltage regulator is also turned
off. When PM2 is entered, a power-down sequence is run.
PM2 is typically entered when using the Sleep Timer as the wakeup event, and also combined with
external interrupts. PM2 should typically be choosen, compared to PM1, when expected sleep time
exceeds 3 ms. Using less sleep time does not reduce system power consumption compared to using
PM1.

4.1.4 PM3

PM3 is used to achieve the operating mode with the lowest power consumption. In PM3, all internal
circuits that are powered from the voltage regulator are turned off (basically all digital modules; the only
exceptions are interrupt detection and POR level sensing). The internal voltage regulator and all oscillators
are also turned off.
Reset (POR or external) and external I/O port interrupts are the only functions that operate in this mode.
I/O pins retain the I/O mode and output value set before entering PM3. A reset condition or an enabled
external I/O interrupt event wakes the device up and places it into active mode (an external interrupt starts
from where it entered PM3, whereas a reset returns to start-of-program execution). The content of RAM
and registers is partially preserved in this mode (see
power-up sequence as PM2.
PM3 is used to achieve ultralow-power consumption when waiting for an external event. It should be used
when expected sleep time exceeds 3 ms.
4.2

Power-Management Control

The required power mode is selected by the MODE bits in the SLEEPCMD control register and the
PCON.IDLE bit. Setting the SFR register PCON.IDLE bit enters the mode selected by SLEEPCMD.MODE.
An enabled interrupt from port pins or Sleep Timer or a power-on reset wakes the device from other power
modes and brings it into active mode.
When PM1, PM2, or PM3 is entered, a power-down sequence is run. When the device is taken out of
PM1, PM2, or PM3, it starts at 16 MHz and automatically changes to 32 MHz if CLKCONCMD.OSC was 0
when entering the power mode (setting PCON.IDLE). If CLKCONCMD.OSC was 1 when PCON.IDLE was
set, when entering the power mode, it continues to run at 16 MHz.
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Power Management and Clocks
Section
Copyright © 2009–2014, Texas Instruments Incorporated
4.6). PM3 uses the same power-down and
SWRU191F – April 2009 – Revised April 2014
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