User Manual

System overview
Communication principles
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BACnet
BACnet (Building Automation and Control Networks) is a communications protocol for building automation
and control networks. BACnet ensures the interoperability between devices from different manufacturers.
See http://en.wikipedia.org/wiki/BACnet.
VendorID
Each BACnet device has a VendorID to identify the manufacturer. The VendorID for the Siemens BACnet
system devices is 7.
BACnet over Ethernet/IP
Applications on the management level can interact via standard IT network services concurrently to BACnet
services.
Desigo supports BACnet/IPv4 and BACnet/IPv6 (via PXG3.M/L router). IPv6 to IPv4 is NOT compatible.
The parallel operation of IPv4 and IPv6 is possible with the use of a PXG3.L/M BACnet router.
See http://de.wikipedia.org/wiki/IPv6.
Network performance
The performance of the network depends on the following criteria:
● Number of devices on the bus
● Segmentation of the topology via routers (for LonTalk bus)
● Number of simultaneously active clients
● Peer-to-peer communication resulting from distributed PX applications
● Other communications services using the same transmission medium, where, e.g., office
communication on a separate VLAN share the same IP trunk
● Application download on the network
Due to these factors, which can vary widely from project to project, it is not possible to make any
generalized statements about network performance. If the specified product quantities are adhered to,
performance is adequate.
If the network performance is not satisfactory, the following actions may help:
● Use the same automation station for items of equipment with frequent process interaction.
● Divide the network into segments via BACnet router and an Ethernet/IP backbone.
● Isolate the automation station from the network when downloading an application.
BACnet and IP network structuring
BACnet supports various application services which are transmitted to all BACnet devices (broadcasts).
Global broadcasts are blocked by the IP router. BACnet solves this problem by using a BACnet Broadcast
Management Device which ensures that IP broadcasts only appear in one IP segment. The logical BBMD
functionality can be configured in every BACnet router and in every PX automation station with BACnet/IP.
One BBMD can be configured per BACnet/IP port. Devices with BBMD must have a static IP address.
BACnet over MS/TP
MS/TP stands for Master Slave / Token Passing. Each device on the link is considered the master when it
has the token. If it does not have immediate need to use the token, it passes the token along to the next
device. All devices on the link which do not currently have the token are regarded as slaves, and listen to
any messages the current master may have for it. As all devices take turns being master, the link is
effectively peer-to-peer.
Use of other network technologies
IP networks (besides the other technologies mentioned above) provide the network infrastructure Desigo
devices are connected to. In case a Desigo installation is spatially distributed (e.g., several buildings on a
campus, multiple branches in a country) the connection of these local IP networks (LANs) normally is done
using a Wide Area Network (WAN) or a point-to-point transmission line. These can be based on non-IP
technologies but typically are transparent for IP traffic. In this way, all the BACnet devices connected via an
IP network can communicate with each other.