How to use IO Buffer with defined location in VHDL?
The information you have provided for the timing and comms interface seems to be for the link between the sender and the ADF4158 device.  If you wanted to read the data from the IO Buffer on the Micro Blaze, you would have to suss out the interface between the IO Buffers and the sender.

From the first diagram you posted it looks as though that interface might be one way, that is to say that data can be sent from the Microblaze to the IO buffer and then to the sender, in which case the IO buffer that the data is sent to is determined by the software on the Microblaze rather than external control signals.

If you want any more help figuring out how to control the interface between the microblaze and the sender then post some details about the interface and we can go from there.

Hope this has helped.