Networking
Master/slave networks
Digi XBee® 3 802.15.4 RF Module User Guide
111
If
A1
is
0x06
(bit 0 clear, bit 1 set, and bit 2 set), then the active scan will accept a beacon from any
channel, providing the PAN ID matches. This is useful if the PAN ID is known, but not the channel.
If
A1
is
0x07
(bit 0 set, bit 1 set, and bit 2 set), then the active scan will accept a beacon from any PAN
ID and from any channel. This is useful when the network does not matter, but the one with the best
signal is desired.
Whenever multiple beacons are received that meet the criteria of the active scan, then the beacon
with the best link quality is selected. This applies whether
A1
is
0x04
,
0x05
,
0x06
, or
0x07
.
Before the End Device joins a network, the Associate LED will be on solid. After it joins a network, the
Associate LED will blink twice per second. You can also query the association status with
or by observing modem status frames when the end device is operating in API
mode.
If association parameters are changed after the end device is associated, the end device will leave the
network and re-join in accordance with the new configuration parameters.
After an end device successfully joins a network, the
DH
and
DL
parameters on the device are updated
to point towards the address of the coordinator it associated with. This allows communication to the
coordinator to occur automatically in Transparent mode, and ensures that indirect messaging poll
requests are sent to the correct address—see
Direct and indirect transmission
.
Additionally, after associating, an end device has
set to
0xFFFE
, indicating
that the newly associated end device should use its 64-bit address. After associating, if you want a 16-
bit address for the end device, set
MY
again.
Note
MY
is reset to
0xFFFE
if the end device needs to leave and re-associate with the coordinator.
If a coordinator changes channel or PAN ID, the end device is not informed of the change and indicates
that it is still associated. You can set
on the end device to force it to leave
the network and attempt to join again, validating that the end device can still communicate with the
coordinator.
Coordinator association
A device becomes a coordinator and allows association if
CE
is 1 and
A2
has bit 2 set. See the following
table and
.
Bit
Hex value
Meaning
0
0x01
Allow PAN ID reassignment
1
0x02
Allow channel reassignment
2
0x04
Allow association
By default,
A2
is 0, which prevents devices from associating to the coordinator. So, if
CE
is
1
and
A2
bit
2 is
0
, the device still creates a network, but end devices are unable to associate to it.
Note
In this configuration, depending on the value of
the device might send
messages indirectly—see
Direct and indirect transmission
If
A2
bit 2 is set, then joining is allowed after the coordinator forms a network.
If
A2
bit 0 is set, the coordinator performs an active scan. The active scan process sends a beacon
request to the broadcast address (0xFFFF) and the broadcast PAN ID (0xFFFF) and listens for beacons
responses. This process is repeated for each channel specified in
SC
.