800xA Profibus DP topology with alternating slaves
I have AC800M PM860 with S800 I/O connected via ModuleBus. Now I have to extend the system with additional devices controlled via Profibus DP.
I need to add master communication unit (CI854A?) to the controller.
Slave devices are alternating; 4 slave devices are physically connected to the bus but only 2 are active (power supplied) at the time. I think commonly used Profibus DP line topology is not possible in this case.
What kind of network topology I should apply with Profibus DP slaves and which components I need to set it up?
Thank you for your help!
Voted best answer
The last profibus slave with its terminator switched "ON" must be powered up. This is an essential condition for the proper functioning of metalic profibus otherwise the whole profibus segment communication is down.
I suggest to use any Profibus Hub in your configuration.
Or you can use 2 profibus connectors on CI854 master as "simple profibus hub" since both connectors of CI854 are electrically isolated (they work like separate profibus segments and must be terminated each) but these 2 segments logically form common Profibus network. In other words AC800M CPU can see all slaves defined in hardware tree under CI854 independently of slave connection to the first or second connector of CI854. Of course an address of each slave connected to CI854 must be unique.