
Transmission, addressing, and routing
Multicast transmissions
XBee/XBee-PRO® S2C ZigBee® RF Module
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Binding table
Each router and coordinator maintain a persistent binding table to map source endpoint and cluster
ID values into 64 bit destination address and endpoint values. The capacity of the binding table is 16
entries.
Multicast transmissions
XBee modules use multicast transmissions to broadcast a message to destination devices that have
active endpoints associated with a common group ID. The device handles an explicit transmit request
frame (0x11) using the Multicast Tx Option (0x08) as a multicast transmission request.
Address resolution
The 64 bit destination address value does not matter and we recommend that it be set to
0xFFFFFFFFFFFFFFFF. Set the 16 bit destination address value to the destination groupID.
Fragmentation
Each unicast transmission may support up to 84 bytes of RF payload, although enabling security or
using source routing can reduce this number. For more information, see
. However, the XBee ZigBee firmware supports a ZigBee feature called fragmentation
that allows a single large data packet to be broken up into multiple RF transmissions and
reassembled by the receiver before sending data out its serial port.
The transmit frame can include up to 255 bytes of data broken up into multiple transmissions and
reassembled on the receiving side. If one or more of the fragmented messages are not received by
the receiving device, it drops the entire message, and the sender indicates a transmission failure in
Applications that do not wish to use fragmentation should avoid sending more than the maximum
number of bytes in a single RF transmission (see
If you enable RTS flow control on the receiving device (using the
D6
command) it receives a
fragmented message, it ignores RTS flow control.
Note
Broadcast transmissions do not support fragmentation. Maximum payload size = up to 84 bytes.
Data transmission examples
This section provides examples for data transmission using AT and API firmware.