I feel like inserting here that I discovered a way for genesis controllers to be used on this system. Since this thread comes up in google i figure its a good place to post this.
After a bit of sleuthing, educated guess work, poking, and frustration i have gotten Genesis controllers working on the PF3 Plus, as well as probing out the controller pinouts for the tct-6035.
I've done this work as I'm interested in making an ultra-micro genesis that takes carts, as i've done for the famicom here.
I'll be adding pictures of ICs with the pinouts later including for the tct6035, but for now pictures and a short explanation.
The IC on the bottom of the genesis portion is the converter chip for snes -> genesis. Starting with the red wire (+5) its P1 - select, A/B, up, down, left, right, start/c | P2 follows the same format for the next 7 pins. This side is from/to the tct-6035. The other side of this chip goes to the controller ports. I didn't map these out as i did not care. I think you could use this to create a snes to genesis adapter if you really wanted to.
My next step is to un-mix the the left/right audio channels.