Specifications
XBee®/XBee‐PRO®SERFModules
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a number of sleep periods have expired (SN sleep periods). This mechanism allows the XBee to
wake at regular intervals to poll its parent for data without waking an external device for an
extended time (SP * SN time). This is shown in the figure below.
Note: SP controls the packet buffer time on routers and coordinators. SP should be set on all
router and coordinator devices to match the longest end device SP time. See the XBee Router /
Coordinator Configuration section for details.
Extended Cyclic Sleep
In extended cyclic sleep operation, an end device can sleep for a multiple of SP time which can
extend the sleep time up to several days. The sleep period is configured using the SP and SN
commands. The total sleep period is equal to (SP * SN) where SP is measured in 10ms units. The
SO command must be set correctly to enable extended sleep.
Since routers and coordinators can only buffer incoming RF data for their end device children for
up to 30 seconds, if an end device sleeps longer than 30 seconds, devices in the network need
some indication when an end device is awake before they can send data to it. End devices that use
extended cyclic sleep should send a transmission when they wake to inform other devices that
they are awake and can receive data. It is recommended that extended sleep end devices set SO
to wake for the full ST time in order to provide other devices with enough time to send messages
to the end device.
Similar to short cyclic sleep, end devices running in this mode will return to sleep when the sleep
timer expires, or when the SI command is received.
Transmitting RF Data
An end device may transmit data when it wakes from sleep and has joined a network. End devices
transmit directly to their parent and then wait for an acknowledgment to be received. The parent
will perform any required address and route discoveries to help ensure the packet reaches the
intended destination before reporting the transmission status to the end device.
Receiving RF Data
After waking from sleep, an end device sends a poll request to its parent to determine if the parent
has any buffered data for it. In pin sleep mode, the end device polls while the Sleep_RQ pin is de-
On/Sleep
Δt = SP
Δt = SP * SN
(SN = 1)
Setting SN > 1 allows the XBee to silently poll for data without asserting On /Sleep. If RF data is received
when polling, On/Sleep will immediately assert .
Transmitting poll request to parent
Δt = SP
Sleep_RQ
Transmitting Poll
Request
Legend
Δt = SP * SN
On/Sleep
(SN = 3)
Transmitting poll request to parent