Sleep modes
About sleep modes
XBee 868LP RF Modules User Guide
84
About sleep modes
A number of low-power modes exist to enable devices to operate for extended periods of time on
battery power. Use the
SM
command to enable these sleep modes. The sleep modes are
characterized as either:
n
Asynchronous (
SM
= 1, 4, 5).
n
Synchronous (
SM
= 7, 8).
Asynchronous modes
n
Do not use asynchronous sleep modes in a synchronous sleeping network, and vice versa.
n
Use the asynchronous sleep modes to control the sleep state on a device by device basis.
n
Do not use devices operating in asynchronous sleep mode to route data.
n
We strongly encourage you to set asynchronous sleeping devices as end-devices using the
CE
command. This prevents the node from attempting to route data.
Synchronous modes
Synchronous sleep makes it possible for all nodes in the network to synchronize their sleep and wake
times. All synchronized cyclic sleep nodes enter and exit a low power state at the same time.
This forms a cyclic sleeping network.
n
A device acting as a sleep coordinator sends a special RF packet called a sync message to
synchronize nodes.
n
To make a device in the network a coordinator, a node uses several resolution criteria through
a process called nomination.
n
The sleep coordinator sends one sync message at the beginning of each wake period. The
coordinator sends the sync message as a broadcast and every node in the network repeats it.
n
You can change the sleep and wake times for the entire network by locally changing the
settings on an individual device. The network uses the most recently set sleep settings.
Normal mode
Set
SM
to 0 to enter Normal mode.
Normal mode is the default sleep mode. If a device is in this mode, it does not sleep and is always
awake.
Use mains-power for devices in Normal mode.
A device in Normal mode synchronizes to a sleeping network, but does not observe synchronization
data routing rules; it routes data at any time, regardless of the network's wake state.
When synchronized, a device in Normal mode relays sync messages that sleep-compatible nodes
generate, but does not generate sync messages itself.
Once a device in Normal mode synchronizes with a sleeping network, you can put it into a sleep-
compatible sleep mode at any time.
Asynchronous pin sleep mode
Set
SM
to 1 to enter asynchronous pin sleep mode.
