S7 driver, basics

The WinCC OA S7 driver is a native driver for connection to the periphery with Siemens S7 PLCs. The driver can communicate with S7-300, S7-400, S7-1200 and S5 series. The native S7 driver can be used under Windows, Linux and Solaris for

Sending data to the PLC.
Polling data from the PLC.
Receiving spontaneous data from the PLC. For this purpose you must use the extension TSPP (Time Stamped Push Protocol) or cyclic services.
Receiving and acknowledging S7 alarms

The protocol used for this driver is the so called ”S7 messaging” the telegrams are transported via TCP/IP. S7 messaging is the protocol that Siemens applications also use for communication. As opposed to the Fetch/Write protocol, for example, it is possible to encode data for several data blocks in one telegram.

Considering redundancy with WinCC OA and the periphery the following cases can be covered with the S7 driver in WinCC OA:

WinCC OA can be redundant.
Each WinCC OA system can have one or more network cards for the communication with the PLCs.
Each WinCC OA system can have one or two connections to each PLC.
Each WinCC OA system can communicate with two redundant PLCs (either in one redundant PLC or two PLCs).

Client/Server and Master/Slave

In normal operation the S7 driver will be the master in the communication as usual for a SCADA system. This means that the communication requests are sent by the S7 driver.

The S7 driver also supports the Slave mode for the TSPP extension (in this case it is also possible to receive spontaneous data from the PLC). The establishment of the TCP/IP connection for a TSPP connection is also done by the driver.

Layer model

The S7 driver in WinCC OA was implemented with ACCON-AGLink, a toolkit from Deltalogic. The programmed API of ACCON-AGLink and the DLL from this toolkit is the interface between WinCC OA / S7 driver and the periphery / S7 PLCs. The ACCON-AGLink provides the following functions:

Configuration of the connections
Establish / close the connections to the PLCs
Send data to the PLCs
Poll data from the PLCs
Alive check for the used connections

For the communication with a S7 PLC the S7 messaging protocol via TCP/IP is used. The advantages of this protocol are:

Mixed data (data with different data types) can be sent in one telegram
Data in different DBs can be sent in one telegram

The design of the connection to the periphery via ACCON-AGLink consists of the following layers:

Chapter	Description
S7 driver, basics	Introduction and links to other chapters.
Requirements and installation	Requirements and installation of the S7 driver.
Configuration of the S7 driver	The connection to the periphery (S7-300/S7-400/S7-1200) is established via this panel.
Multi Point Interface - Configuration	Description of the configuration parameters of a connection over MPI.
Time Stamp Push Protocol - Configuration	Description of the configuration parameters of a connection over TSPP.
S7 Alarms	Description on how to map S7 alarm classes to WinCC OA alarm classes, to receive alarms and to acknowledge them.
Use and configuration of the S5 driver	The use and configuration of the S5 driver.
Symbolic addresses	Description of using symbolic addresses with the S7 driver.
Redundant connection or device	Detailed information about redundant peripheral devices and connections.
Defining the peripheral addresses of the S7 driver	Panel for configuring peripheral addresses.
Possible config entries of the S7 driver	Description of the config entries for the S7 driver.
Internal data points of the S7 driver	Data point elements of the internal data points.
Details on the S7 driver	Description of the debug levels, transformations, alive mechanism and further important information.
Tips & Troubleshooting	Further tips for configuring the peripheral connection with the S7 driver.
Summary and relevant links	Summary and links to other relevant chapters in this Online Help.

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