Transmission, addressing, and routing Fragmentation
Digi XBee® 3 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.
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 NP (Maximum Packet
Payload Bytes). 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
Transmit Status frame - 0x8B.
Applications that do not wish to use fragmentation should avoid sending more than the maximum
number of bytes in a single RF transmission (see Maximum RF payload size.
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.
Send a packet in Transparent mode
To send a data packet in Transparent mode (AP = 0), set the DH and DL commands to match the 64-
bit address of the destination device. DH must match the upper 4-bytes, and DL must match the lower
4 bytes. Since the coordinator always receives a 16-bit address of 0x0000, a 64-bit address of
0x0000000000000000 is the coordinator's address (in Zigbee firmware). The default values of DH and
DL are 0x00, which sends data to the coordinator.
Example: Send a transmission to the coordinator.
In this example, a '\r' refers to a carriage return character.
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