I have started working on a Z80 board that would use only 3 parts (Z80, RAM, Glue logic+SIO).
The Glue is done via a PSoC4 from a Cypress CY8CKIT-049-42xx (<5 euros…) – Currently the Flash chip is not used, and only 64KB from the RAM (128K) is used. Z80 is clocked at 9.6Mhz.
There is provision for RAM & ROM bank switching in the future (or not… maybe it would be better to replace the flash by an sdcard)
It has started working… If you count the serial-to-usb chip on the CY8CKIT, that’s a 4 chips Z80 board – if you count the CY8CKIT as one chip, it is a 3 chips board…
With Z80′s reset line low, via a bootloader, Grant Searle’s Basic is sent from the PSoC4 memory to the RAM and the Z80′s reset is set to high.