4 Parts (Z80,RAM,Psoc4,SDCARD) Z80 SBC

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My target has been to create a functional Z80 board using minimum parts while being able to run Grant Searle’s binaries WITHOUT modifications.

It fits on a single breadboard :

The PSoC provides :

– Reset, clock (initially @ 9.6Mhz, Z80 now tested OK at 12Mhz)
– Address decoding (not really used) and potentially RAM bank switching
– Bootloader transfer to RAM that allows boot via Sdcard (file ‘rom.bin – FatFs used)
– Wait signal generation during IO requests – Int acknowledge (iorq + m1) – IM2 supported.
– SIO emulation – CY8CKIT’s CY7C65211 also convert rs232 to USB as a bonus.
– FlashCard emulation that maps requests to a file (cpm.bin) on sdcard.

Currently the code works almost fine, except the SIO that I am not able to use Kermit/xmodem in cpm2.2 – still investigating.

Even using the CY8CKIT-049-42xx with its bootloader, the code size is <22k and uses around 3k RAM.

Schematic :

Psoc design :

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