XB24-BPDK Digi International/Maxstream, XB24-BPDK Datasheet - Page 19

• Manufacturer Part Number: XB24-BPDK
• Description: KIT DEVELOPMENT XBEE SERIES 2
• Manufacturer: Digi International/Maxstream
• Series: XBee™r
• Type: 802.15.4/Zigbeer

Specifications of XB24-BPDK

• Frequency: 2.4GHz
• For Use With/related Products: XBee™ Series 2 Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

XBee ZNet 2.5/XBee‐PRO ZNet 2.5 ZigBee OEM RF Modules v1.x4x
discover the level of RF activity on different channels (energy scan), and to discover any nearby
operating PANs (PAN scan). Energy Scan
When a coordinator comes up for the first time, it performs an energy scan on multiple channels
(frequencies) to detect energy levels on each channel. Channels with excessive detected energy
levels are removed from its list of potential channels to start on.
Figure 3‐02. Potential Channels
List of Potential Channels
1
2
3
4
. . .
14
15
16
Performing an energy scan allows the coordinator to avoid
starting on channels with high energy levels.
PAN Scan
When the energy scan completes, the coordinator scans the remaining quiet channels (found in
the energy scan) for existing PANs. To do this, the coordinator sends a broadcast, one-hop beacon
request. Any nearby coordinators and routers will respond to the beacon request by sending a
beacon frame back to the coordinator. The beacon frame contains information about the PAN the
sender is on, including the PAN identifier (PAN ID), and whether or not the device is allowing
joining. (The PAN scan is more commonly called an active scan or a beacon scan.)
Figure 3‐03. PAN Scans
PAN Scan
Beacon Request
Beacon Request
Beacon Request
New
Router
Coordinator
Coordinator
Beacon
Beacon
A PAN Scan allows the coordinator to detect nearby PAN IDs to avoid
duplicating existing PAN IDs
Once the coordinator has completed the energy and PAN scans, it parses all received beacons and
attempts to start on an unused PAN ID and channel. When the coordinator starts a PAN, it can
then allow routers and/or end devices to join the PAN. A coordinator retains the channel and PAN
ID attributes through power cycle or reset events.
3.3. Joining a PAN
Router and end device types must discover and join a ZigBee PAN. To do this, they first issue a
PAN scan, just like the coordinator does when it starts a PAN. From the PAN scan, the router or
end device receives a list of beacons from nearby ZigBee devices. The router or end device parses
this list to find a valid ZigBee network to join.
© 2008 Digi International, Inc.
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