Programming S7-200 PLC via modem


Thread Starter

Eric Mok

I have followed the steps in Step 7 MicroWin32 to set up the modems, unfortunately my modems are NOT on included in the list of MicroWin and therefore I have to punch it the modem initialization strings. I am using a GVC 56K modem and I can't find the appropriate init string for it, can anybody help?

Moreover, do I need to program the remote modem (that attached to the PLC) to answer and set up a connection to the the dial-in from the programming station (PC)?

Please send me any material and/or articles on PLC communications via modem.

Any help is appreciated.

Contact your local Siemens office and ask for a copy of the S7-200 Tips and Tricks - it is free! In there is an application using modems and the S7200 and may explain how to do this. Also I remember there was an issue with the S7200 that required you use 11bit modems, but I think that may have been for the 21x series S7200 and now they are selling 22x series.


Jimmy Miller

I have only used the Modem option with one of the Multi-Techs listed in Micro-Win. It was seamless . . . just plug and play. I tried to use 2 US Robotics modems and ran into the same problems you did. Good luck. hey guys in Johnson City are really helpful, but only if you use one of their recommended units. Sorry!

Alejandro (Alex) Flores

I have accomplished this in several projects. I has however been awhile. I used the exact modem outlined. I think it was a "MultiModem" it was about $225 USD. These are special modems. I think the Siemens documentation mentions the need for a either a 10 or 11 bit modem. Some off the shelf modems do no support this. If yours does you may have a chance configuring it.You may have to link you modem cable to another PC to determine the "hayes Commands" being issued by Step Seven. After that you will need to compare them with the command list that your modem has. The multi modem has several NON Hayes commands. If Step7 sends such a string to a modem that does not have that command. THe modems recourse may be to reject the entire string. Linking it to a PC instead may allow you to interpret them and then select the appropriate ones in your modem. May be the main question may be is my time worth less then $225 x2
for the modems. How all goes well with you.
Alejandro FLores
[email protected]