3: ZigBee Software Architecture > Application Concepts

Application Concepts

This page introduces some concepts at the Application level that will help you to understand the more detailed software architecture presented in the rest of this module.

Endpoints

A node may have several applications running on it - for example, a node in an environment monitoring network may be measuring temperature and humidity, each of which is an application. These application instances on a node are said to be endpoints, where messages can originate and terminate.

In order to route messages arriving at the node to the appropriate application, each application on the node must be uniquely identified and is given an endpoint address. Endpoint addresses for user applications are numbered from 1 to 240. Therefore, to identify a particular application instance in a ZigBee network, you need to supply the relevant network address and then the required endpoint address on the node.

	Endpoint address 255 can also be used. This is the broadcast endpoint address - the same data can be sent to all applications on a node by sending the message to this endpoint address.

ZigBee Device Objects (ZDO)

Endpoint address 0 on each node is reserved for a special application called the ZDO (ZigBee Device Objects). This application has a number of roles, including defining the type of node (Co-ordinator, Router or End Device), initialising the node and participating in network creation. You will learn more about the ZDO later in the course.

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