Product manual

TAC Xenta Server – Gateway, Technical Manual B Protocols
Schneider Electric Buildings AB, June 2011 159 (184)
04-00124-06-en
B.6.1 BACnet PTP Networks
The BACnet Point To Point protocol allows two nodes to communicate
over either a dedicated RS-232 serial connection or a modem. In either
case, each node is termed a half-router because together they are able to
route messages between 2 BACnet networks using the RS-232 or
modem link. In practice, however, even nodes that do not connect to a
BACnet network can still exchange values using the PTP protocol.
Although the Xenta 913 communicates using the PTP link, it does not
itself act as a device on the BACnet network (that is, other BACnet
devices or host applications cannot access the Xenta 913 directly). But
once the Xenta 913 has successfully connected to the target half router
it continuously polls the target devices to read the required object values
for use within a control system. It can also write the necessary control
system values out to the target devices.
Each target device must have a unique numeric address on the network.
Device addresses can be in the range 1 to 255. The maximum number
of devices that can be attached to the target network varies according to
its type (see the documentation supplied with the target half-router and
devices for more information).
Note
• The target half-router need not be physically connected to a
device network. It can instead be a stand-alone device, or can
appear as multiple pseudo devices, so that it can exchange values
using the BACnet Point To Point protocol.