Sleep modes Sleeping routers
XBee®-PRO 900HP/XSC RF Modules
57
Synchronization messages
A sleep coordinator regularly sends sync messages to keep the network in sync. Unsynchronized
nodes also send messages requesting sync information.
Sleep compatible nodes use Deployment mode when they first power up and the sync message has
not been relayed. A sleep coordinator in Deployment mode rapidly sends sync messages until it
receives a relay of one of those messages. Deployment mode:
n Allows you to effectively deploy a network.
n Allows a sleep coordinator that resets to rapidly re-synchronize with the rest of the network.
If a node exits deployment mode and then receives a sync message from a sleep coordinator that is in
Deployment mode, it rejects the sync message and sends a corrective sync to the sleep coordinator.
Use the SO (sleep options) command to disable deployment mode. This option is enabled by default.
A sleep coordinator that is not in deployment mode sends a sync message at the beginning of the
wake cycle. The sleep coordinator listens for a neighboring node to relay the sync. If it does not hear
the relay, the sleep coordinator sends the sync one additional time.
A node that is not a sleep coordinator and has never been synchronized sends a message requesting
sync information at the beginning of its wake cycle. Synchronized nodes which receive one of these
messages respond with a synchronization packet.
If you use the SOcommand to configure nodes as non-coordinators, and if the non-coordinators go six
or more sleep cycles without hearing a sync, they send a message requesting sync at the beginning of
their wake period.
The following diagram illustrates the synchronization behavior of sleep compatible devices.
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