Specifications

XBee®/XBee‐PRO®SERFModules
©2009DigiInternational,Inc. 74
Sleep Period
The sleep period is configured based on the SP, SN, and SO commands. The following table lists
the behavior of these commands.
The XBee module supports both a short cyclic sleep and an extended cyclic sleep that make use of
these commands. These two modes allow the sleep period to be configured according to the
application requirements.
Short Cyclic Sleep
In short cyclic sleep mode, the sleep behavior of the module is defined by the SP and SN
commands, and the SO command must be set to 0x00 (default) or 0x02. In short cyclic sleep
mode, the SP command defines the sleep period and is settable up to 28 seconds. When the XBee
enters short cyclic sleep, it remains in a low power state until the SP time has expired.
The Smart Energy specification recommends a nominal sleep cycle of between 7.5 and 60 seconds
to mitigate congestion due to poll requests between an end device and its parent while
maintaining an adequate poll rate. The default SP setting is 0x2EE, or 7.5 seconds.
After the sleep period expires, the XBee sends a poll request transmission to its parent to
determine if its parent has any buffered data waiting for the end device. Since router and
coordinator devices can buffer data for end device children up to 30 seconds, the SP range (up to
28 seconds) allows the end device to poll regularly enough to receive buffered data. If the parent
has data for the end device, the end device will start its sleep timer (ST) and continue polling to
receive data. If the end device wakes and finds that its parent has no data for it, the end device
can return to sleep immediately.
The SN command can be used to control when the On/Sleep line is asserted (high). If SN is set to
1 (default), the On/Sleep line will be set high each time the XBee wakes from sleep. Otherwise, if
SN is greater than 1, the On/Sleep line will only be set high if RF data is received, or after SN wake
cycles occur. This allows an external device to remain powered off until RF data is received, or until
Com-
mand
Range Description
SP
0x20 - 0xAF0 (x 10 ms)
(320 - 28,000 ms)
Configures the sleep period of the module.
SN
1 - 0xFFFF
Configures the number of sleep periods
multiplier.
SO
0 - 0xFF
Defines options for sleep mode behavior.
0x02 - Always wake for full ST time
0x04 - Enable extended sleep (sleep for full
(SP * SN) time)
DIN
A cyclic sleep end device enters sleep mode when no serial or RF data is received for ST time .
ST = Time Awake
On/Sleep
Legend
On/Sleep
Transmitting Poll
Request