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:

• Asynchronous (SM = 1, 4, 5).
• Synchronous (SM = 7, 8).

Asynchronous modes

• Do not use asynchronous sleep modes in a synchronous sleeping network, and vice versa.
• Use the asynchronous sleep modes to control the sleep state on a device by device basis.
• Do not use devices operating in asynchronous sleep mode to route data.
• 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.

• A device acting as a sleep coordinator sends a special RF packet called a sync message to synchronize nodes.
• To make a device in the network a coordinator, a node uses several resolution criteria through a process called nomination.
• 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.
• 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.