XBee®/XBee‐PRO® ZB SMT RF Modules
The application should always update the 16-bit address in the address table when one of these frames is
received to ensure the table has the most recently known 16-bit address. If a transmission failure occurs,
the application should set the 16-bit address in the table to 0xFFFE (unknown).
Fragmentation
Each unicast transmission may support up to 84 bytes of RF payload. (Enabling security or using source
routing can reduce this number. See the NP command for details.) However, the XBee ZB 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. This is shown in
the image below.
The transmit frame can include up to 255 bytes of data, which will be 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, the receiver will drop the entire message, and the sender will indicate a transmission
failure in the Tx Status API frame.
Applications that do not wish to use fragmentation should avoid sending more than the maximum number
of bytes in a single RF transmission. See the "Maximum RF Payload Size" section for details.
If RTS flow control is enabled on the receiving module (using the D6 command) and a fragmented message
is received, then RTS flow control will be ignored.
Data Transmission Examples
AT Firmware
To send a data packet in transparent mode, the DH and DL commands must be set 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 defined as the coordinator's address (in ZB firmware). The default values of DH
and DL are 0x00, which sends data to the coordinator.
Example 1: Send a transmission to the coordinator.
(In this example, a '\r' refers to a carriage return character.)
A router or end device can send data in two ways. First, set the destination address (DH and DL
commands) to 0x00.
1. Enter command mode ('+++')
2. After receiving an OK\r, issue the following commands:
a. ATDH0\r
b. ATDL0\r
c. ATCN\r
3. Verify that each of the 3 commands returned an OK\r response.
4. After setting these command values, all serial characters will be sent as a unicast transmission
to the coordinator.
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DCD [ DIGITAL CORE DESIGN ]
