Well, the model is a CP341, but there are several types depending on which protocol modbus uses. Mine is Modbus RTU RS 232. You need to know this. I am not back to work till Tuesday, but if you look at a Siemens automation catalogue on line, the card is under communications.
You also need to know if it is a master or a slave. Mine is a master. In theory, you have to order the correct one, but I didn't. I ordered a "Slave" but wanted a "Master".
A quick call to Siemens automation UK, and they told me the dongle should work (It plugs in the back). And it does!They just emailed me a link to their "Master " drivers.
There are some sample programs in the library that comes with "Step 7".
I used theirs, and just modified it. I have only one slave, but the slave cannot address all the registers at once, so I just have a cycling program that calls the relevant datablocks/registers. I think the Siemens will do over 100. What do you actually want to do?
I hope this isn't too vague?
Markie