Data exchange in isochronous mode s7-1500T/Sinamics

Hi,

I have s7-1500T CPU and two SINAMICS V90 PN connected. I am learning about data exchange in isochronous mode. I have found two documents which I am using to learn it. The first one is from this link https://support.industry.siemens.com/cs/ww/en/view/109480489 at page 4 of pdf, and the second one is from cycles and response times (isochronous mode section). In first document in description  of process of exchange (number 3 ) it says "Then the digitized measured value is transferred in the distributed IOs via the backplane bus from the input module to the header module.", How does it correspond to my case? I don't have distributed I/O like ET 200SP, are drives also distributed I/Os? Also in second document it says "Transport of input data to the IO controller/DP master (CPU) via the subnet" at number 3 of description. But from pictures of data exchange in first document, all data is provided before send clock, and in second picture it is provided after (picture in attachment). I thought that in motion control, MC-Servo is called at the beginning of send clock, so data should be provided before send clock?

In brief, how does data exchange goes when i am using only two drives? The number 3 in description of that process is confusing me the most. 

Also, do I use backplane bus when I have only drives and plc

Hello,

3.2.12.3 Operational Sequence and Timeouts

https://support.industry.siemens.com/cs/ww/en/view/109749262