The protocol is described in Chapter 2: of the User Guide at the URL link below.
https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/ug_vip.pdf

Considering handshake communication + packet transfer, it is an image of checking "out" and "not out" with "start of packet" and "end of packet" signals as triggers.

One example of a debugging technique is to combine SignalTap II with OnchipMemory (relatively small amount), monitor the transferred data, and additionally observe various signals (ready, valid, data, etc.) to improve the resolution during operation. , i/p, etc. can be checked.