Digi International Inc XBEEPRO2 Manual Do Utilizador

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XBee®/XBee‐PRO® ZB RF Modules 
© 2011 Digi International, Inc.
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In the figure above, t1, t2, and t3 represent the following events:
•T1 - Time when Sleep_RQ is asserted (high)
•T2 - Time when the XBee enters sleep (CTS state change only if hardware flow control is enabled)
•T3 - Time when Sleep_RQ is de-asserted (low) and the module wakes.
The time between T1 and T2 varies depending on the state of the module. In the worst case scenario, if the end 
device is trying to join a network, or if it is waiting for an acknowledgment from a data transmission, the delay 
could be up to a few seconds.
When the XBee is awake and is joined to a network, it sends a poll request to its parent to see if the parent has 
any buffered data for it. The end device will continue to send poll requests every 100ms while it is awake.