This is what it looks like right now. The left-most chip on the right board is the ATF22LV10C SPLD, next to the memory. The left board is a Raspberry pi Pico that together with 4 74LVC244 buffers form a 32-bit input bank. The Pico has only 26 usable GPIO, which is not really enough for what I need. Maybe more on that in the future.

The Pico runs a very simple program that reads CLK/RW/address/data from the 65C02 and the outputs from the SPLD so I can see what goes on as I single-step the clock from the Teensy. It is very useful to have a static CPU like the 65C02 that CAN actually work at human-readable speeds!