Each 1-Wire device has a unique serial number assigned at the time of manufacture. Once a device is mounted to a circuit board, or an iButton is placed on a physical object, it would be helpful to associate that device's 1-Wire Network Address numbers with a physical object.

Tagging therefore attempts to establish a relationship between a 1-Wire device and some other object, and provide enough information to enable accessing the services offered by that device.

Tagging is perhaps most meaningful when applied to 1Wire chips mounted on circuit boards, or iButtons which are attached to an object such as a machine or a crate of goods. Mobile iButtons could contain tagging information if they are "attached" to a carrier such as a person. In this case the tagging information could include your name, some account or access number, etc.

The association of the 1-Wire ID number to the physical object could be placed in some kind of database. A group of devices can be located together and share some common purpose. This group is termed a cluster. The cluster tag can contain information which applies to the cluster as a whole, while each device in the cluster could also contain tagging information.

One example is the Systronix 8x1-Wire I/O board (click for a photo) which has four DS2406 dual switches. There is no correlation between the 1-Wire IDs of each DS2406 and its position on the board. Each DS2406 is connected to one pushbutton and one LED. If you press one of the four pushbuttons, you'd like software to be able to determine if you pressed S1, S2, S3 or S4. Software would also like to be able to light a specific LED. You could have multiple such boards on a 1-Wire network. Each board is a cluster. When you detect that a pushbutton is pressed, you'd like to know not only its switch position but its cluster.

The tagging information can reside in a database located on the 1-Wire master or it could be placed in the memory of a 1-Wire device. The DS2406 has 1 kbit of available OTP memory, which is ideal. Each switch and LED can identify itself. Not all 1-Wire devices have such memory. An additional 1-Wire device can be mounted on the cluster either as a chip or an iButton in a socket.

By carrying the 1-Wire tagging data with the sensor cluster, it can be self-configuring when presented to a new master application. If it is impractical or not desired to keep the 1-Wire tagging data with the cluster, it must reside elsewhere. The master application can then take one of the unique 1-Wire Network Address numbers found on a 1-Wire device to request the appropriate 1-Wire tagging data from the database source.