Digi XBee Product Manual

XBee / XBee-PRO networks
XBee / XBee-PRO RF Modules 802.15.4 Product Manual 26
Coordinator start-up
Coordinator power-up is governed by the A2 (Coordinator Association) command. On power-up, the
Coordinator undergoes the following sequence of events:
1. Check A2 parameter- Reassign_PANID flag
Set (bit 0 = 1) - The Coordinator issues an Active Scan. The Active Scan selects one channel and
transmits a request to the broadcast address (0xFFFF) and broadcast PAN ID (0xFFFF). It then listens
on that channel for beacons from any Coordinator operating on that channel. The listen time on each
channel is determined by the SD (Scan Duration) parameter value.
Once the time expires on that channel, the Active Scan selects another channel and again transmits
the BeaconRequest as before. This process continues until all channels have been scanned, or until 5
PANs have been discovered. When the Active Scan is complete, the results include a list of PAN IDs
and Channels that are being used by other PANs. This list is used to assign an unique PAN ID to the
new Coordinator. The ID parameter will be retained if it is not found in the Active Scan results.
Otherwise, the ID (PAN ID) parameter setting will be updated to a PAN ID that was not detected.
Not set (bit 0 = 0) - The Coordinator retains its ID setting. No Active Scan is performed.
2. Check A2 parameter - Reassign_Channel flag (bit 1)
Set (bit 1 = 1) - The Coordinator issues an Energy Scan. The Energy Scan selects one channel and
scans for energy on that channel. The duration of the scan is specified by the SD (Scan Duration)
parameter. Once the scan is completed on a channel, the Energy Scan selects the next channel and
begins a new scan on that channel. This process continues until all channels have been scanned.
When the Energy Scan is complete, the results include the maximal energy values detected on each
channel. This list is used to determine a channel where the least energy was detected. If an Active
Scan was performed (Reassign_PANID Flag set), the channels used by the detected PANs are
eliminated as possible channels. Thus, the results of the Energy Scan and the Active Scan (if
performed) are used to find the best channel (channel with the least energy that is not used by any
detected PAN). Once the best channel has been selected, the CH (Channel) parameter value is
updated to that channel.
Not set (bit 1 = 0) - The Coordinator retains its CH setting. An Energy Scan is not performed.
3. Start Coordinator
The Coordinator starts on the specified channel (CH parameter) and PAN ID (ID parameter). Note,
these may be selected in steps 1 and/or 2 above. The Coordinator will only allow End Devices to
associate to it if the A2 parameter “AllowAssociation” flag is set. Once the Coordinator has
successfully started, the Associate LED will blink 1 time per second. The LED is solid if the Coordinator
has not started.
4. Modifying a Coordinator
Once a Coordinator has started:
Modifying the A2 (Reassign_Channel or Reassign_PANID bits), ID, CH or MY parameters will cause the
Coordinator’s MAC to reset (The Coordinator RF module (including volatile RAM) is not reset).
Changing the A2 AllowAssociation bit will not reset the Coordinator’s MAC. In a non-beaconing
system, End Devices that associated to the Coordinator prior to a MAC reset will have knowledge of
the new settings on the Coordinator. Thus, if the Coordinator were to change its ID, CH or MY settings,
the End Devices would no longer be able to communicate with the non-beacon Coordinator. Once a
Coordinator has started, the ID, CH, MY or A2 (Reassign_Channel or Reassign_PANID bits) should not
be changed.

Digi XBee Specifications

General

Operating Frequency	2.4 GHz
RF Data Rate	250 kbps
Model	XBee S2C
Category	Control Unit
Operating Voltage	2.1 to 3.6V DC
Operating Temperature	-40 to +85 °C
Interface	UART
Dimensions	24.38 x 27.61 x 9.14 mm