The final PCB just arrived - assembled, and tested. Looking good. I am now using the free GPIO (28) from the Pico to pull down the Microprofessor's WAIT line low. Previously, to power cycle the Microprofessor, I needed to hold down the Microprofessor's RESET button to prevent it from accessing the SRAM emulation before the Pico was up and running. Obviously, it takes a bit of time for the Pico to power up - by the time the SRAM emulation was up and running, the Microprofessor had already crashed if not held in RESET otherwise. Now, upon power cycle / reset, I am pulling down WAIT and it is released when the SRAM emulation is up and running. This allows me to power cycle and reset without having to hold down the Microprofessor's RESET button. The WAIT line is on Pin 37 of the Microprofessor expansion pin header.

The firmware might still get tweaked and improved here and there, but the hardware part of this project is done. I am satisfied with the current revision - of course, it's not perfect, but what is?