The S7 protocol is designed for transfering data into SCADA systems via Ethernet. The PROFINET protocol is used for communication between PLCs and IO modules. The S7 protocol can be used for communication via PROFINET connector in PLC or in add-on communication modules.
The Ethernet brings many advantages as speed, simple wire infrastructure, multiple stations on a single line, standardization, etc.
This communication type can be used for:
PROFIBUS is a physical interface that cannot be directzly connected to the PC. The connection is managed by additional PROFIBUS PC card (or other additional HW).
The MPI (MPI-S7) interface is a "derivate" of the PROFIBUS-DP. The communication line is RS485, the speed rate is preset to 187.5kb/sec. The speed rate can be decreased to 19.2kb/sec and according to the device (CPU300, OP, CP6511) it can be even increased to 12Mb/sec.
The PPI interface is used for the Simatic S7-200 PLCs. It is a serial interface (so no special HW card is needed).
For the communication with the SIMATIC devices that dispose of the ASCII serial communication interface it is necessary to know the description of the ASCII protocol on the Simatic side.
The communication over the programming PG port on the Simatic. The communication is of the point-to-point type (1PC-1Simatic) via the computer's serial port. For more Simatic devices it is possible to use the multi-port communication card on PC. The speed rate is 9600 Bd at the most. The communication is suitable for transfers not demanding quick answers.
These protocols for serial link RS232 support some Simatic devices directly and there is possible to purchase a communication module for these protocols for some PLC's.
These protocol types are considered very obsolete.
PmS7 - Driver for communication by the S7-TCP/IP protocol communicates with the PLCs via the Ethernet protocol S7. If the PLC is equipped by the PROFINET connector, then the driver can be used (for example S7-1200, ET-200S, some types of S7-300 and S7-400).
PLCs without the PROFINET connector can be modified in order to enable the PROFINET connectivity, for example.
For easy integration of this driver into the application it is handy to use:
Virtually all mentioned communication types can be executed via the OPC server. In the PROMOTIC application the PmOpcClient object is then used - See also Communication by OPC interface. There are many OPC server manufacturers. Below you can fing a short list.
This OPC server is supplied by default with the PLC programming environment or it can be purchased in its software package SOFTNET, etc. The OPC server (or its variants) supports virtually all protocols required for the communication with the PLCs of the Simatic type (serial link, MPI, PROFIBUS, PROFINET, PPI, SinecH/L, etc.).
The description of the OPC server is outside the scope of this documentation. Just very brief overiew of the two basic ways of data items configuration:
Example: "K3.CPU315(1).db20_Analog.aiEesaGJh" ...
Example: "S7:[S7 connection_1]DB10,INT0,1", "S7:[S7 connection_2]DB4,X0,0,1", S7:[S7 connection_2]DB20,REAL42" ...
The Softing company (http://www.softing.com) is an OPC server manufacturer. The company also manufactures a HW converter NETlink PRO (Ethernet Gateway for MPI/PROFIBUS).
The Kepware company (http://www.kepware.com) is a manufacturer of universal OPC server, that is used not only for Simatic PLCs, but also a wide spectrum of other PLCs.