Siemens OP17 & IM308-C


Thread Starter


We have a Siemens 135U using an IM308-C as master of a profibus network that contains 2 OP17. Siemens gave us a FB58 to do the interface between the IM and the OP's and a DB (DB-ZU) where we define 2 DB's that will serve as areas of interface. The problem is that only one OP is working.Each group of 16 words of DB-ZU is for a specific equipment.We are using the 4th and 5th group for the 2 OP's.The OP that has assigned the 4th area is the one that works.If we change the assignment then it's the other one that works.Never the two at the same time as it should be. Can somebody help us on this one?

Hakan Ozevin

In a Profibus network, any slave can have a *unique* master that can read and write; the other masters can only read. The OP's can only be masters, therefore maybe your problem is attaching several slaves to several masters.
If you inform about your configuration (how many slaves, which master they are logically-not electrically- connected) and your problem in details (are'nt the OP working for any slave or any master?), maybe I can give more suggestions.

Good luck,

Hakan Ozevin

Graham Wilcox

I have used the IM308C to talk to remote I/O.

We had two racks, both had inputs and outputs.

Each rack and the inputs and outputs had to be read/written to separately
using the comms FB

i.e. Two racks = four calls to the FB
1. Read rack one
2. Write rack one
3. Read rack two
4. Write rack two

NOTE: Only one FB call was allowed to be active at a time, so we had to
write some logic to step throught the different calls one at a time
i.e. call FB to read rack one, do not write rack one or talk to rack two at
all. Next scan (or when FB indicates finished, I forget) call FB to write
to rack one but do not read rack one or talk to rack two at all. etc

Graham Wilcox