Configuring a step 7 network with an "extra" profibus master PLC for commissioning?

oregonsam

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Configuring a step 7 network with an "extra" profibus master PLC for commissioning?

We're installing a system with many remote control enclosures containing profibus remote racks. The main PLC is a S7 400 in the main control enclosure.
I was thinking about configuring the network to include a "cheap" s7300 master to just use for commissioning. That way I could verify that the s7 400's network & hardware are correct without the network installed. Just power up an enclosure, hook the 300 PLC & my laptop to the remote rack and use monitor/modify to test the I/O. I was hoping that the "fancy" programming profibus connectors might allow me to plug straight in without messing with wiring.

Anyway, if anybody has any comments or already does this I would appreciate any advice or warnings.
Thanks,
Sam
 
Yes, you can definitely do as you propose.

To connect laptop, S7-300 master and profibus slave you should have a cable with profibus connector with a PG socket in the CPU end, and without a PG socket in the slave end. Then keep that cable for the next time you have to do something similar.
 
Will the "missing" commissioning CPU cause problems with normal operation?

Thanks for the response.
Is there any way to keep the "unused" master from causing bus faults or problems with the system when it isn't being used?
 
Aha. Maybe i have misunderstood your initial post.
I though you would hook up the S7-300 master and the new slave completely separate from the existing system.
"Just power up an enclosure, hook the 300 PLC & my laptop to the remote rack and use monitor/modify to test the I/O"

Your last post seems to indicate that you intend to connect the Profibus network as it is intended to be in the end, but not to configure the new slave in the S7-400 master.
That is also doable. Be warned that changing a Profibus network from monomaster to multimaster increases the bus cycle time by an approximate factor 10.
Configure a STEP7 project with both the S7-400 and the S7-300 as masters in the same Profibus network.
Then configure the new slave to the S7-300. Compile everything in NetPro, and then download to both S7-400 and S7-300. You will have to restart the S7-400. In this way you have prepared the Profibus token rotation time to take both S7-300 and the new slave into account.
Next you must hook up everything. Put the S7-300 that you intend to remove later as the last node. Be aware that the S7-300 must be either powered up or disconnected from the Profibus (previous node termination is set to ON) so that the terminator resistors are with power.

A more simple way would be to test the new slave with the S7-300 without it being on the same Profibus network as the S7-400.
When that goes OK, then configure the slave with the S7-400, but without it being accessed from the user program. Have OB86 included, and in CPU Properties Cycle/Clock memory set "No OB85 Callup". When you then connect the slave to the S7-400's Profibus network, you can then see if the new slave gets connected as it shall. And you can test it by forcing outputs for example.
 

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