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Digi XBee® 3 802.15.4 RF Module User Guide
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Work with Legacy devices
The Legacy 802.15.4 device (S1 hardware) transmits packets one by one. It does not transmit a
packet until it receives all expected acknowledgments of the previous packet or the timeout expires.
The XBee/XBee-PRO S2C 802.15.4 and XBee 3 802.15.4 RF Modules enhance transmission by
implementing a transmission queue that allows the device to transmit to several devices at the same
time. Broadcast transmissions are performed in parallel with the unicast transmissions.
This enhancement in the XBee/XBee-PRO S2C 802.15.4 and XBee 3 802.15.4 RF Modules can produce
problematic behavior under certain conditions if the receiver is a Legacy 802.15.4 module (S1
hardware).
The conditions are:
n
The sender is an XBee 3 802.15.4 RF Module, and the receiver is a Legacy 802.15.4 module.
n
The sender has the Digi header enabled (
MM
= 0 or 3) and
RR
(XBee Retries) > 0.
n
The sender sends broadcast and unicast messages at the same time to the Legacy 802.15.4
module without waiting for the transmission status of the previous packet.
The effect is:
n
The receiver may display duplicate packets.
The solution is:
n
Set bit 0 of the
C8
(802.15.4 compatibility) parameter to 1 to enable TX compatibility mode in the
XBee 3 802.15.4 RF Module. This eliminates the transmission queue to avoid sending to multiple
addresses simultaneously. It also limits the packet size to the levels of the Legacy 802.15.4
module.
For information on the specific differences between an XBee 3 and Legacy 802.15.4 devices, refer to
the
