Sleep modes
Asynchronous pin sleep mode
XBee/XBee-PRO DigiMesh 2.4 RF Module User Guide
60
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.
Pin sleep allows the device to sleep and wake according to the state of the SLEEP_RQ pin (pin 9).
When you assert SLEEP_RQ (high), the device finishes any transmit or receive operations and enters a
low-power state.
When you de-assert SLEEP_RQ (low), the device wakes from pin sleep.
Asynchronous cyclic sleep mode
Set
SM
to 4 to enter asynchronous cyclic sleep mode.
Cyclic sleep allows the device to sleep for a specific time and wake for a short time to poll.
If the device receives serial or RF data while awake, it extends the time before it returns to sleep by
the specific amount the
ST
command provides. Otherwise, it enters sleep mode immediately.
The ON_SLEEP line (pin 13) is asserted (high) when the device wakes, and is de-asserted (low) when
the device sleeps.
If you use the
D7
command to enable hardware flow control, the CTS pin asserts (low) when the
device wakes and can receive serial data, and de-asserts (high) when the device sleeps.
Asynchronous cyclic sleep with pin wake up mode
Set
SM
to 5 to enter asynchronous cyclic sleep with pin wake up mode.
This mode is a slight variation on asynchronous cyclic sleep mode (
SM
= 4) that allows you to wake a
device prematurely by asserting the SLEEP_RQ pin (pin 9).
In this mode, you can wake the device after the sleep period expires, or if a high-to-low transition
occurs on the SLEEP_RQ pin.
Synchronous sleep support mode
Set
SM
to 7 to enter synchronous sleep support mode.
A device in synchronous sleep support mode synchronizes itself with a sleeping network, but does not
sleep itself. At any time, the node responds to new nodes that attempt to join the sleeping network
with a sync message. A sleep support node only transmits normal data when the other nodes in the
sleeping network are awake.
Sleep support nodes are especially useful:
n
When you use them as preferred sleep coordinator nodes.
n
As aids in adding new nodes to a sleeping network.
Note
Because sleep support nodes do not sleep, they should be mains powered.
