DS2409T

The DS2409T MicroLAN coupler is an essential component to build and control 1-Wire MicroLAN networks with multi-level branching. In contrast to approaches that switch the ground line, the coupler DS2409T maintains a common ground level for the whole network and keeps the inactive segments powered. This simplifies supplying central or local power for additional circuitry and prevents loss of status of parasitically powered devices. It also avoids disrupting communication caused by the parasitic power supply of 1-Wire devices after activating a branch. The coupler DS2409T does not contain any user-programmable memory. To label a branch, one can connect any 1-Wire memory device to the auxiliary 1-Wire output of the coupler. Both the main and the auxiliary 1-Wire output are supported by a "smart-on" command. This command generates a reset/presence sequence on the selected output before the electronic switch closes the contact to the 1-Wire bus. This way the bus master can apply a ROM function command (optionally followed by a memory function) to the devices on the just activated segment with all other devices DS2409T in the network remaining deselected. This significantly speeds up the analysis of topology and population in a continuously changing network. The coupler also supports the bus master in detecting arrivals on the inactive segments of the network by responding to the conditional search command. The control output of DS2409T can be used to optically signal the on/off state of a branch or, together with the auxiliary output, for handshaking in dual-master applications. The network size can be maximized by using a DS2480 line driver at the bus master's serial interface. The DS2480 compensates for the rising ground level caused by the non-zero on-resistance of couplers in multi-level networks.