The CP 343-1 BACnet independently handles data traffic via Industrial Ethernet and BACnet protocol. The module has its own processor and can be put into service directly using the unique preset Ethernet address (MAC) via the network.

Due to the support of the dynamic host configuration protocol (DHCP), the IP address can be assigned from a central DHCP server.

The CP 343-1 BACnet works in multi-protocol mode for the following communication services:

• PG/OP communication
  PG/OP communication allows all S7 stations connected to the network to be remotely programmed.
  • S7 routing;
    using S7 routing it is possible to use PG communication across networks.
• S7 communication
• Open communication (SEND/RECEIVE)
• A large number of stations can be accessed thanks to the multicast function
• Use of the socket interface in the partner system possible without RFC 1006
• Integral autocrossover function permits use of uncrossed connecting cables
• BACnet communication based on TCP/IP, BACnet server according to EN 16484, Part 5

Siemens completes its building control system DESIGO with the SIMATIC S7. DESIGO S7 introduces two new performance packages to building automation:

• Building Solution
• Building Integration

These enable projects to be implemented for "Industrial Building Automation" where programmable logic controllers (PLCs) are required at the automation level.

The DESIGO S7 Building Solution performance package permits the use SIMATIC S7 within a DESIGO system (control system for building automation) with an S7-HVAC library (Heating, Ventilation and Air Conditioning), that is based on the library of DESIGO PX. Communication with the DESIGO system is by means of BACnet. This permits efficient engineering of HVAC applications.

With DESIGO S7 Building Integration, existing SIMATIC S7 (software without HVAC library) components are efficiently integrated into a DESIGO system by means of BACnet communication.

BACnet communication

Based on TCP/IP, a BACnet server compliant with EN 16484, Part 5 is made available. The CP processes the protocol autonomously as far as possible so that the CPU is not burdened with the BACnet protocol. The CP 343-1 BACnet optionally supports:

• BACnet communication for any SIMATIC software by mapping SIMATIC data onto BACnet
• HVAC functions with BACnet communication by using corresponding function blocks;
  these HVAC function blocks are a component of the block library and are to be incorporated in the S7 user program.

Linear structure with CP 343-1 BACnet with integral switch

BACnet consists of:

• Standardized services that are processed autonomously by the CP
• Standardized objects that present a user view of the automation

The actual configuration of the BACnet objects and their mapping to S7 data is performed by a BACnet mapping tool.

The configuration data of the BACnet objects generated by the mapping tool can be downloaded to the SIMATIC S7 using the general download function or using Delta download. The mapping tool can be obtained free of charge from your local Siemens I BT office.

The standardized transport protocol UDP is used for BACnet, as it already has sufficient transport checking mechanisms available. Like TCP, UDP is a transport protocol, but unlike TCP it operates on a connectionless basis. BACnet devices may only work with the UDP port number permanently assigned to them. The UDP port number 47808 = 0xBAC0 is registered for BACnet.

The Ethernet IP addressing consists of the IP address, the subnet mask and the default gateway. BACnet devices within one subnet have the same subnet address. In the case of devices with integral BBMD functionality (BACnet Broadcast Management Device), e.g. DESIGO automation stations, DHCP – the automatic assignment of IP addresses in networks – is generally not permitted.

BACnet uses broadcast messages for the communication, i.e. all devices are addressed directly. As a rule, Ethernet IP routers block these broadcast messages so that a direct connection of Ethernet subnets is not possible. By using BBMD, broadcast messages can still be distributed.

Diagnostics

Extensive diagnostics options are available via NCM, including:

• Operating status of the CP
• General diagnostics and statistics functions
• Connection diagnostics
• LAN controller statistics
• Diagnostic buffer

Diagnostic options during operation

• Integration into network management systems through the support of SNMP V1 MIB-2 objects;
  this allows the current status of the Ethernet interface to be called up, e.g. for network management.

Configuration

STEP 7 V5.4 SP5 or higher and NCM S7 for Industrial Ethernet (supplied with STEP 7 V5.x) plus a hardware support package (HSP) are required for configuring the CP 343-1 BACnet. The configuration data of the CP is stored on the CPU. This means a module can be replaced without a PG.
An additional "Building Integration" runtime license (reference number S55372-C107) is required in order to use the BACnet protocol on the module. Please contact your regional Siemens representative for ordering the license.