5
Examining Sleep Mode
5.1
Purpose
Sleep mode can be enacted by either the Wireless CPU® or the Host at any time. The
primary purpose for enabling sleep mode is to conserve energy (current
consumption). This feature is particularly useful for applications which power the
Wireless CPU® through a battery. Minimising current consumption extends the
periods between charges and subsequently lengthens battery life.
Similarly, even if the Wireless CPU® is active, the Host processor may wish to conserve
power if it has no reason to communicate with the Wireless CPU®. The Host
processor could initiate sleep and revert to a low power state.
5.2
Current Consumption
If the Host application initiates sleep in order to conserve power consumption in the
Host processor it does not necessarily mean that the Wireless CPU® will go to sleep.
Events and processes running on the Wireless CPU® may continue even though there
is no need to communicate to the Host. These activities could include network paging
events, embedded application script execution, various IO activity (status LED, for
example), etc.
For users wishing to calculate battery life, or determine battery capacity, examples of
battery life for various operating scenarios are given in the Integrators Manual.
However, it is important for you to anticipate the degree of activity for your specific
application to make accurate battery life calculations. The lowest Wireless CPU®
current consumption is achieved when the master clock is switched off and the device
is in a DRX mode of network operation. Even though the execution of embedded
application scripts may not require Host communication or network communication
(other than periodic paging), the baseband will consume much more current than the
simple case of idle mode where all non-essential functions are suspended.
Therefore, any activity performed by the Wireless CPU® has to be factored in to your
power consumption calculations.
For lowest power consumption, we recommend that you disable all unneeded
alternate I/O functions. The activity LED can be disabled using the AT*E2LED=0
command.
APPLICATION NOTE
GR/GS64 UART Sleep Protocols
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