Transmission, addressing, and routing Transmission timeouts
XBee/XBee-PRO ZigBee RF Modules User Guide 72
To ensure the end device has adequate time to wake and receive the data, the extended transmission timeout to
an end device is:
(50 * NH) + (1.2 * SP)
This timeout includes the packet buffering timeout (1.2 * SP) and time to account for routing through the mesh
network (50 * NH).
If an acknowledgment is not received within this time, the sender will resend the transmission up to two more
times. With retries included, the longest transmission timeout when sending data to an end device is:
3 * ((50 * NH) + (1.2 * SP))
The SP value in both equations must be entered in millisecond units. The SP command setting uses 10 ms units
and must be converted to milliseconds to be used in this equation.
For example, suppose a router is configured with NH=30 (0x1E) and SP=0x3E8 (10,000 ms), and that it is either
trying to send data to one of its end device children, or to a remote end device. The total extended timeout to the
end device is about:
3 * ((50 * NH) + (1.2 * SP)), or
3 * (1500 + 12000), or
3 * (13500), or
40500 ms, or
40.5 seconds.
Transmission examples
Example 1: send a unicast API data transmission to the coordinator using 64-bit address 0,
with payload TxData
API frame:
7E 0014 10 01 00000000 00000000 FFFE 00 00 54 78 44 61 74 61 AB
Field composition:
0x0014 - length
0x10 - API ID (tx data)
0x01 - frame ID (set greater than 0 to enable the tx-status response)
0x00000000 00000000 - 64-bit address of coordinator (ZB definition)
0xFFFE - Required 16-bit address if sending data to 64-bit address of 0.
0x00 - Broadcast radius (0 = max hops)
0x00 - Tx options
0x54 78 44 61 74 61 - ASCII representation of "TxData" string
0xAB - Checksum (0xFF - SUM (all bytes after length))
Description
This transmission sends the string "TxData" to the coordinator, without knowing the coordinator device's 64-bit
address. A 64-bit address of 0 is defined as the coordinator in ZB firmware. If the coordinator's 64-bit address was
known, the 64-bit address of 0 could be replaced with the coordinator's 64-bit address, and the 16-bit address
could be set to 0.
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