No
. 96-1886-01E
Rev
.
1.1
GTECH Aircon Radio (Model GWT154)
PAGE
30
OF
72
Fragmented packets have the fragmentation flag set and are sequenced using a range of index values
above the maximum byte count of the secure 802.15.4 packet. An indexed fragment is assumed to
hold the maximum number of payload bytes. The exception being the end packet in a fragment
sequence where the fragmentation flag is set, but the Index/Length field contains a valid byte count for
the remaining bytes of the packet.
The maximum safe payload is derived from packets using extended addresses and PANs. Networks
using short addressing have the option of reallocating the unused extended address bytes to the payload
field. The fragmentation process described here uses the maximum safe payload length for its
calculations. If a larger encrypted payload length is employed, the calculations need to be adjusted
accordingly.
Figure 16 - Data Fragment Structure
Fragment
Flag (f)
Length /
Index
Fragment
Index
Fragment
Length (n)
0
Length = 0
Radio Configuration
Packet
- -
0
1 <= Length <= 80
-
n = Length
0
81 <= Length <= 111
reserved
-
n = Length
0
112 <= Length <=127
illegal
- -
1
112 (0x70)
0
n = 80
1
113 (0x71)
1
n = 80
1
114 (0x72)
2
n = 80
1
115 (0x73)
3
n = 80
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