Enabling/disabling cyclical communication for profibus slaves
I'd like to disable and enable Profibus slaves dynamically with AC 800F as master (v9.1). I'm thinking of multiple non-stationary devices which can be dynamically connected to the bus when needed and then enabled through Digivis by the operator. If a device is not needed anymore, it can be disabled through Digivis and then disconnected physically. IIRC this kind of setup is possible with several other Profibus masters (e.g. S7-300, HIMatrix F35).
In Freelance, I learned that you can disable and re-enable cyclical communication for any Profibus slave without a "bus member failed" message appearing: In Control Builder F, this can be done manually by toggling the "cyclical communication" checkbox in the online slave configuration (in the hardware tree, see attached picture 01). So far, so good.
I'd like to toggle this function from inside a program, i.e. dynamically enabling and disabling slaves. The documentation shows a block variable for just this checkbox which is writable (MSCYEnable, see attached picture 02), but I'm not sure how to access it. I can't find the value in the variable picking box (F2). Do I need a separate gateway like the help text states? That seems unnecessarily complicated to me.
I'd appreciate suggestions or alternative approaches. Thank you for your thoughts.
When you say "program", do you mean a controller program (like FBD or IL) or do you mean a windows program?
A controller program cannot access Profibus Slave User parameters. Even if you would use an OPC Gateway, because a controler is not an OPC client.
If you want to disable the the slaves from DigiVis or any other Windows program you need to use OPC. For DigiVis as well as other Windows programs you need to configure an OPC Gateway in your project and give Read/Write access for all the HW Objects in the Taglist using the Gateway view of the Taglist. After downloading the configuration to the OPC Gateway (you need to install a Freelance OPC Server and have it running to see the OPC Gateway ressource online) you can use a 3rd party OPC client to browse the Freelance OPC server.
Here I'm not sure whether you would see the objects parameter also in the OPC server or only the Inputs and outputs.
If you see the parameters also, then in principle you can use DigiVis to write via that OPC server to the Profibus Slave parameter.
In order to do that, you would need in addition to above add an OPC-Server (OPC-S) object into your project to be able to use OPC functionality from DigiVis (PLC Integration).
You need to map that OPC-S object to your OPC Gateway from the same project. Then browse that OPC-S object with the Sytsem/OPC Item List dialog and instantiate a variable from that parameter. Then you can use that variable in a FGR display to disable or enable the cyclic transfer towards that slave.