Basics

Addresses

Device Addresses

One aspect that is a little confusing is the distinction between Device addresses and Group addresses. Device addresses are written in the format of 1.1.1 (as can be seen in the image above for "#1 MAXinBOX 16 Plus". They can possibly denote something about where the device is within the topology. As can be seen above this Device (1.1.1) is within Area 1 (the first '1' in 1.1.1), Line 1 (the second '1' in 1.1.1) and is the first device in this Line. In my installation the significance of the Area and Line numbers is not related to where the devices exist, but rather just a way of grouping and organising devices. As such the Area and Line numbers do not assist in knowing where any equipment is located. 

Group Addresses

Group addresses are somewhat of a strange concept when coming to KNX from a IP/Ethernet networking background. They are possibly somewhat like a multicast address for IP/ethernet. The group addresses do not represent a device but rather an address that devices can subscribe to. Essentially data can be written to and read from the bus by devices that subscribe to a particular group address. In the following image the Group Address 0/0/41 is highlighted. On the right-hand side of the image it can be seen that 3 "Group Objects" have been assigned to the Group Address 0/0/41. These exist only in ETS until the details are downloaded to the respective device. Concerning the image below, we can see that the Group Address can be associated with two different devices (3.2.10 and 1.1.1). As such even though the association between Group Addresses are related to Devices (using a setting in ETS which is download to the device) the association between Group Addresses has more directly to do with a Group Object on the device. How this operates in practice I describe further on this page Light On-Off.