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THEORY OF OPERATION
16
64-bit MAC address
The 64-bit MAC address consists of a 40-bit Organizationally Unique Identifier (OUI) and a 24-bit address
programmed by the manufacturer. All ZB2430 transceivers have the same OUI of 0x00 0x00 0x00 0x50 0x67 which
can be used to distinguish Aerocomm devices on a network but cannot be used to route packets throughout the
network.
When a packet needs to be sent to a specific device through the network, the 16-bit network address must be used.
In order to send data to a specific device in the network, the OEM can compile a table which lists the 64-bit MAC and
the corresponding 16-bit Network address (see Table 3 below). The ZB2430’s built-in Discover IEEE Address and
Discover Network Address commands allow the OEM to query the network and discover all available devices that
respond within a fixed period.
Mesh Routing (AODV)
The ZigBee protocol uses the Ad-Hoc On-Demand Distance Vector (AODV) routing algorithm. AODV allows nodes to
pass messages through their neighbors to devices which they cannot communicate directly. This is done by
discovering the routes along which messages can be passed using the shortest route possible.
Figure 4 below shows a typical ZigBee network. The circles surrounding the 4 nodes represent the Personal
Operating Space (POS) of each node. Because of the limited range, each node can only communicate with the
neighboring node(s) next to it. When a node needs to send a message to a node which is not a neighbor, it
broadcasts a Route Request (RREQ) message containing the Source Destination Address, the Network Address of
the Destination radio and a path cost metric.
In the example below, Node 0 needs to send a message to Node 3; however the two are not within communication
range of each other. Node 0’s neighbors are Node 1 and Node 2. Since Node 0 cannot directly communicate with
Node 3, it sends out a RREQ which is heard by Nodes 1 and 2 (see Figure 5: "ZigBee Route Request" on page 17).
ENGINEER’S TIP
16-bit Network Addresses.
In a ZigBee network, nodes are assigned a 16-bit NWK address according to how the network
formed. By design, the Coordinator will always have a NWK address of 0x0000. The first
Router to that associates with the Coordinator is assigned a NWK address of 0x0001. The
second Router that associates with the Coordinator is assigned an address of 0x143E.
The 16-bit address is persistent through power loss and only resets when an NV Reset
command is issued performed or NV Restore is disabled in EEPROM (EEPROM address 0x45,
bit-3).
Table 3: Device Table Example
Index MAC Address (64-bit) NWK Address (16-bit)
0 0x00 0x00 0x00 0x50 0x67 0x12 0x34 0x56 0x0000
1 0x00 0x00 0x00 0x50 0x67 0x16 0x45 0x34 0x0001
2 0x00 0x00 0x00 0x50 0x67 0x34 0x21 0x78 0x143E