Wireless - switchless kernal mod

I can't reply (I tried to both through nabblers and by directly
replying) to the original thread since I registered after the last
mail sent to that thread.

Most of the stuff for the kernal mod targets old c64 boards so I
wanted to take on the 250469 boards on the newest c64 editions. In
these boards kernal + basic is a combined 16K rom.

With a bit of external logic I crammed 7 different kernals and 1 basic
rom into an 27c512 64kx8 bit rom.

https://www.youtube.com/watch?v=mWdeX7mWdNg

The plan is to switch the kernals with the attiny processor on the
attachment board.

The method I chose for doing this is like this,

A program on the c64 carefully modulates a chosen address bit so that
it's certain percentage 1 or 0s for a certain period. Thus it sends a
pilot signal repeatedly for the attiny side to sync and match both the
period and phase of these signal.

The program on the attiny side continously samples one of the address
lines and tries to sync to this pilot signal.

After syncing, which is assumed, c64 program sends the chosen eprom
bank for the selected kernal. Attiny receives this and switches the
kernal.

C64 program is the easiest to write probably. On the attiny side I
don't want to write time critical code. Of course both sides need to
do one unit of work at a roughly constant time. Currently I'm
simulating what I want to do with a multithreaded application on the
pc. One thread for the sending side and another one for the receiver.

Only 4 bits of information will be transferred actually so it doesn't
matter if both sides phase out after that transfer finishes.

The question is, is there any such previous work for an algorithm or
similar for such a syncing job?

Best regards,

Nejat