Hi All,
I'm designing a Profibus interface. I'm a little confused with the +5V termination power supply (Voltage Plus, or VP). My understanding is that VP is supplied by something on a segment that is used to actively terminate all the receivers, and usually these resistors are in the Profibus connectors themselves.
So: Is it the master only that drives VP onto the bus?
If my device can be a master or slave, I presume I have to be able to either drive VP or not depending on whether I'm a master or not (?)
What is the current requirement of VP?
Also, for bog standard RS485 applications I usually use isolated 5V supplies locally on each receiver, and a common signal ground reference linking them. Is that usual with Profibus too?
I guess the master would generate VP referenced to this same common ground signal, I assume using an isolated supply. Which means if I already have an isolated supply as part of the reciever section I could use that directly to drive VP (?)
Sorry for all the questions, I can't seem to find any docs that tie this down.
Mark