Digi XBee User Manual

© 2014 Digi International Inc. 47
XBee/XBee-PRO
®
DigiMesh 2.4 User Manual
Asynchronous Cyclic Sleep Mode (SM=4)
Cyclic sleep allows the module to sleep for a specified time and wake for a short time to poll.
Cyclic sleep mode is enabled by setting the SM command to 4. In cyclic sleep, the module sleeps
for a specified time. If the XBee receives serial or RF data while awake, it will extend the time
before it returns to sleep by the amount specified by the ST command. Otherwise, it will enter
sleep mode immediately. The On_SLEEP
line is asserted (high) when the module wakes, and is
de-asserted (low) when the module sleeps. If hardware flow control is enabled (D7 command),
the CTS pin asserts (low) when the module wakes and can receive serial data, and de-assert
(high) when the module sleeps.
Asynchronous Cyclic Sleep with Pin Wake Up Mode (SM=5)
(SM=5) is a slight variation on (SM=4) that allows the module to be woken prematurely by
asserting the Sleep_RQ pin (pin 9). In (SM=5), the XBee can wake after the sleep period
expires, or if a high-to-low transition occurs on the Sleep_RQ pin.
Synchronous Sleep Support Mode (SM=7)
A node in synchronous sleep support mode will synchronize itself with a sleeping network, but
will not sleep itself. At any time, the node will respond to new nodes which are attempting 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 when used as preferred sleep coordinator nodes and as aids in adding new nodes to a
sleeping network.
Note: Because sleep support nodes do not sleep, they should be mains powered.
Synchronous Cyclic Sleep Mode (SM=8)
A node in synchronous cyclic sleep mode sleeps for a programmed time, wakes in unison with
other nodes, exchanges data and sync messages, and then returns to sleep. While asleep, it
cannot receive RF messages or read commands from the UART port. Generally, sleep and wake
times are specified by the SP and ST respectively of the network’s sleep coordinator. These
parameters are only used at start up until the node is synchronized with the network. When a
module has synchronized with the network, its sleep and wake times can be queried with the OS
and OW commands respectively. If D9 = 1 (ON_SLEEP
enabled) on a cyclic sleep node, the
ON_SLEEP
line asserts when the module is awake and de-assert when the module is asleep.
CTS is also de-asserted while asleep (D7 = 1). A newly-powered unsynchronized sleeping node
will poll for a synchronized message and then sleep for the period specified by SP, repeating this
cycle until it becomes synchronized by receiving a sync message. Once a sync message is
received, the node synchronizes itself with the network.
Note: Configure all nodes in a synchronous sleep network to operate in either Synchronous
Sleep Support Mode or Synchronous Cyclic Sleep Mode. Asynchronous sleeping nodes are not
compatible with synchronous sleep nodes.

Digi XBee Specifications

General

Brand	Digi
Model	XBee
Category	Control Unit
Language	English