Siemens S5 and S7 communication protocols 1

[ceit]

Hi,

I need to communicate with S5 and S7 models via the serial RS232 port of my PC into an application which I'm programming in C language. Is it possible to get information about the communications protocols used by both models?. Thanks.

 

[moggie]

The S5 PLC's uses a TTY interface (20mA) there is a converter to change the RS232 on your PC into the TTY for the S5 PLC.

The S7 300/400 uses a MPI interface.
The S7 200 uses a PPI interface.
Both are based on the RS484(?) protocols, again there are interfaces available for both of these PLC's.
One of the best I have seen is the interface from Process-Informatik.
This detects the S7 plc (200/300/400) it is connected to and chabges protocols automatically.

http://www.process-informatik.de

Hope this helps.

 

[ceit]

Thanks moggie,

Another thing,

If I'm usig an Embedded Web-Server to communicate with these PLC's, would you tell me how I could get additional information about the low level protocols for S5 and S7?

By means of low level protocols I refer to those commands I directly must send from and receive to via serial port for establishing a correct connection between Web-Server and PLC.

 

[dloos]

The S5 PLC's require a break signal for 5ms to start communication. To generate the break signal you usually have to use loops in your program. The program then becommes dependend on the PC and the speed your PC is running at. That is why STETP 5 has so many problems with the communication on different platforms and PC's.
If you use a standard interface then you dont't have to worry about the break signal.
INAT ECHOLINK converter with up to 5 serial ports connect to S7-200/300 and S5 PLC's.
The ECHOLINK connects to the Ethernet Network and an OPC Server on your PC (connected to this network)is your entry point (standard windows DDE routines)for programming or SCADA.
Check out

http://www.inat.de