Siemens USS for S7 PLC and MM4 Drive

Hi everybody,

Can any one tell me how can I communication S7-400 PLC with Siemens MM4 VFD? It is very important.I know S7 200 can communicate with MM4 via USS by using some standard instructions, but this time I need to read/write MM4 parameters via USS from S7 400 PLC.

Thanks in advace.

Hello Apel;

First, if you can use Profibus-DP with your drive and your CPU, you will find it much more easier to establish comms between the two. Here is a link to an earlier post on plcs.net regarding this issue:

http://www.plctalk.net/qanda/printthread.php?t=25739

If you must use USS, then look at the foolowing possibilities:
-Drives ES blocks for USS:
http://www2.sea.siemens.com/NR/rdonlyres/94907391-14BA-49EB-90E6-F928E9C68C87/0/DriveESShortStartupInstructions.pdf
-USS and Profibus-DP standards:
http://electronica.li2.uchile.cl/CNC/Masterdrives%20%20MC/5.4.1%20DPV1%20Documentation/Dpv1-b%20-%20Acyclic%20Parameter%20Exchange%20-%20Profibus%20DP.pdf

You will need a serial CP on the S7-400 rack (CP441-2) to establish comms over USS protocol.
Hope this helps,
Daniel Chartier

hi Daniel Chartier,

Thanks.I think your links are valuable.I am going through it.Lets try.

Regards,

dchartier said:

You will need a serial CP on the S7-400 rack (CP441-2) to establish comms over USS protocol.

Click to expand...

A much less expensive alternative is an ET200S 1SI module with USS protocol (6ES7 138-4DF11-0AB0). Of course, you need to use ET200S.
Still, I agree that to use Profibus is overall the simplest and possibly even the cheapest too. The Profibus module for the Micromaster is surprisingly cheap.

Hi Jesper,

Thanks.I have setup S7-400 system with CP.I am trying using USS only. I undarstand that Profibus is better solution, but when system is already installed I cant change it to Profibus..is not it?

Wow, so you have already gotten the CP441 + USS loadable driver !
What did that cost you ?

I think that USS with an S7-200 and a MM4 is smart because an S7-200 supports USS directly on its serial ports, and the MM4 has USS on its onboard terminal strip. At least thats how I understand it. Thus you dont have to purchase anything extra to establish comms between an S7-200 and an MM4.
However, you will find that with S7-300 and S7-400, everything is focused on Profibus. I guess that a CP441 + loadable driver costs more than several S7-200 PLCs !

hi Jesper,
I agree with you.