Digi XBee3 802.15.4 User Manual

Networking Maximum payload
Digi XBee3® 802.15.4 RF Module User Guide
68
Factor
Effect on
maximum
payload Comment
Destination
address
Reduce by 6 This penalty only applies if sending to a long address rather than a
short address.
App header Reduce by 4 The app header for encryption is 4 bytes long. This penalty only applies
if MM = 0 or 3.
Because of the two mandatory reductions when using encryption, no packet can exceed 116 - (5+6)
=105 bytes. The other options may further reduce the maximum payload to 101 bytes, 99 bytes, or 95
bytes.
When operating in API mode and not using encryption, if the source address is long, the receiving
device outputs an RX Indicator (0x80) frame for received data. But, if the source address is short, the
receiving device outputs a Receive Packet (0x81) frame for received data. These same rules apply for
encryption if MM is 0 or 3. This is possible because the four-byte encryption App header includes the
short address of the sender and the long received address is not used for API output. If encryption is
enabled with MM of 1 or 2, then no App header exists, the source address is always long, and the
receiving device in legacy API mode (AP = 2)always outputs a RX Packet: 64-bit Address frame - 0x80.
Maximum payload
The absolute maximum payload size for an 802.15.4 packet is 116 bytes. Depending on module
configuration, the actual maximum payload size will be reduced.
If you attempt to send an API packet with a larger payload than specified, the device responds with a
Transmit Status frame (0x89 and 0x8B) with the Status field set to 74 (Data payload too large). When
operating in transparent mode, if you attempt to send data larger than the maximum payload size,
the data will be packetized and sent as multiple over-the-air transmissions. For more information, see
Serial-to-RF packetization.
Maximum payload rules
1. If you enable transmit compatibility (C8) with the Legacy 802.15.4 module (S1 hardware):
n There is a fixed maximum payload of 100 bytes
n The rest of the rules do not apply. They apply only whenyou disable transmit
compatibility with the Legacy 802.15.4 module.
2. The maximum achievable payload is 116 bytes. This is achieved when:
n Not using encryption.
n Not using the application header (MM is set to 1 or 2).
n Using the short source address.
n Using the short destination address.
3. If you are usingthe application header, the maximum achievable payload is reduced by:
n 2 bytes if not using encryption (EE = 0)
n 4 bytes if using encryption (EE = 1)
4. If you are using the long source address (MY = 0xFFFE),the maximum achievable payload is
reduced by 6 bytes (size of long address (8) - size of short address (2) = 6).

Digi XBee3 802.15.4 Specifications

General

Brand	Digi
Model	XBee3 802.15.4
Category	Control Unit
Language	English