Andy said” You titled the Thread, "Parallel Async Communication Protocol" - so yes, you did say that the Protocol is Async.”
I still say that protocol is async. I said very clearly as you quoted that communication between FIFOs and 8051 is not async but communication between 8051s is async and the protocol is async.

Andy said “Actually, your problem is that you are confusing the the Protocol with the hardware implementation of the interface.”
Hardware implementation is part of a protocol

the hardware implementation is Layer-1, and this protocol is Layer-2, and the two can be treated independently.”
Yes hardware is the first layer of a protocol but a protocol may have much more that two layers, for example it may have many software layers. As I said I don’t want to argue about meanings of terms. You may consider the hardware layer and software layer that I’ve mentioned as a package not protocol! OK, but please focus your criticisms on technical drawbacks of those layers, protocol or whatever you call it, not criticizing why I called the thread “parallel async communication protocol”. If you want to address technical issues (like what are drawbacks of cross checking compared to using supervisor chip,……) as I said I welcome all criticisms but If you want to continue to argue without any technical conclusion, I respectfully say, thank you for your time.

Regards,
Ebrahim Vakilpour