User's Manual

XBee®/XBee‐PRO®ZBRFModules
©2009DigiInternational,Inc. 28
any nearby operating PANs (PAN scan). The process for selecting the channel and PAN ID are
described in the following sections.
Channel Selection
When starting a network, the coordinator must select a "good" channel for the network to operate
on. To do this, it performs an energy scan on multiple channels (frequencies) to detect energy
levels on each channel. Channels with excessive energy levels are removed from its list of
potential channels to start on.
PAN ID Selection
After completing the energy scan, the coordinator scans its list of potential channels (remaining
channels after the energy scan) to obtain a list of neighboring PANs. To do this, the coordinator
sends a beacon request (broadcast) transmission on each potential channel. All nearby
coordinators and routers (that have already joined a ZigBee network) will respond to the beacon
request by sending a beacon back to the coordinator. The beacon contains information about the
PAN the device is on, including the PAN identifiers (16-bit and 64-bit). This scan (collecting
beacons on the potential channels) is typically called an active scan or PAN scan.
After the coordinator completes the channel and PAN scan, it selects a random channel and
unused 16-bit PAN ID to start on.
Security Policy
The security policy determines which devices are allowed to join the network, and which device(s)
can authenticate joining devices. See chapter 5 for a detailed discussion of various security
policies.
Persistent Data
Once a coordinator has started a network, it retains the following information through power cycle
or reset events:
•PAN ID
•Operating channel
• Security policy and frame counter values
• Child table (end device children that are joined to the coordinator).
The coordinator will retain this information indefinitely until it leaves the network. When the
coordinator leaves a network and starts a new network, the previous PAN ID, operating channel,
and child table data are lost.
XBee ZB Coordinator Startup
The following commands control the coordinator network formation process.
Networkformationcommandsusedbythecoordinatortoformanetwork.
Command Description
ID Used to determine the 64-bit PAN ID. If set to 0 (default), a random 64-bit PAN ID will be selected.
SC Determines the scan channels bitmask (up to 16 channels) used by the coordinator when forming a
network. The coordinator will perform an energy scan on all enabled SC channels. It will then perform a
PAN ID scan and then form the network on one of the SC channels.
SD Set the scan duration period. This value determines how long the coordinator performs an energy scan or
PAN ID scan on a given channel.
ZS Set the ZigBee stack profile for the network.
EE Enable or disable security in the network.