More fun with CircuitJS:

I made a loopback to ACK the ACK. This gives a rough estimate of the latency and throughput. Note that I use 2 different clocks: 7KHz and 10KHz to test clocking issues. I can't see much though with this system and a more elaborate simulator becomes necessary. I wish I could hook/link custom scripts to add custom probes and features :-D But at least I could test the inter-wire jitter.

What is interesting is that ... This circuit makes no sense !

It's stupid to ACK an ACK, as it creates this "larsen" situation, self-oscillating... Here it helps create the throughput test.

What makes sense is to ACK data data

1. when there is no data to send (but I have no PISO-SIPO yet) or
2.  when the activity timer expires.

This is not wired yet.