ZWIR451x Programming Guide
© 2016 Integrated Device Technology, Inc.
13
April 12, 2016
2.6.3.
Power Modes
The stack supports different modes to reduce the power consumption of the device. In Active Mode, all module
features are available. The Sleep, Stop, and Standby Modes reduce the power consumption by disabling different
module functionalities. Each of the power-saving modes affects the behavior of the MCU and the transceiver and
supports different wake-up conditions.
Table 2.3
Power Modes Overview
Mode
Wakeup
Clock
Context
I/O
Transceiver
Source
Time
MCU Core
Peripherals
Active
On
Retained
As configured
Sleep
Any IRQ
1.8 µs
Off
Retained
As configured
Stop
RTC IRQ
External IRQ
5.4 µs
Off
Off
Retained
As configured
Standby
RTC IRQ
Wakeup Pin
50 µs
Off
Off
Lost
Analog input
Off
1)
Refers to the status of the RAM and peripheral register contents after wakeup – the backup registers of the MCU are always
available.
2)
Clock is enabled for all peripherals that have been enabled by application code and all peripherals that are used by the library.
3)
Can be powered off by application code.
4)
Remains on if peripheral/transceiver is selected as wakeup source.
Active Mode is entered automatically after startup. In this mode, the MCU core and all peripherals used by the
application are running and all functionality is available. The transceiver is typically on but can be switched off
explicitly by a call to
. This mode has the highest power consumption.
In Sleep Mode, the MCU core is disabled but the MCU peripherals are still functioning if required. The transceiver
can be switched on or off. Memory contents and I/O settings remain in the state that was active at the activation
of the Sleep Mode. Waking up from Sleep Mode is possible on any MCU interrupt. After the wakeup event, the
stack continues execution at the position it had been stopped. The power consumption in Sleep Mode is slightly
reduced compared to Active Mode. If more significant reduction of the power consumption is required, the Stop or
Standby Modes should be considered.
Stop Mode provides significant reduction of power consumption while still providing a short wakeup time and
context saving. Depending on the application’s requirements, the transceiver could remain enabled to wake up
the module when a packet comes in (set the transceiver as the wakeup source). By default, the transceiver is
disabled in Stop-Mode. The MCU core and all peripherals of the MCU are disabled in Stop Mode. Wakeup is only
possible by the built-in real-time clock (RTC) or an external interrupt, triggered at any GPIO line. For that, the
external interrupt must be configured appropriately.
Standby Mode is the lowest power mode. In this mode, the MCU is powered off and the transceiver is on standby.
Only the MCU’s internal RTC is running, serving as a wakeup source. Additionally, the external wakeup pin can
be used to wake up the module. After wakeup, the memory contents of the MCU are lost and must be reinitialized
the same as after normal power-on.