This is a simple adapter enabling the use of RC2014 and RCBus boards with the Zeal 8-bit computer external port or backplane, with optional port mapping.

Port mapping is important because many RCBus boards use ports larger than 0x80, which is reserved I/O space on the Zeal 8-bit computer.

To make the board compatible with Zeal 8-bit, any of the A7-A4 address lines can be inverted -- see online configuration tool. Bit invert is implemented using 74HCT86 (quad 2-input XOR gate).

Tested with:

• SC729 – RCBus Compact Flash Module (with Zeal 8-bit OS)
• SC725 – RCBus Serial and Timer Module (with RomWBW)
• 16C2552 dual UART for RC2014 (with RomWBW)
• (to be added)

No guarantee that it will work with other RCBus boards, but it should be compatible with most of them.

Schematics, BOM and KiCad project are available in GitHub.

Note: in most cases, using a 40-pin socket for connecting RCBus boards is sufficient and easier to use than an 80-pin socket, especially if you need to connect and disconnect frequently. An 80-pin socket is only required if your RCBus board actually uses the NMI, WAIT, BUSRQ, BUSACK, HALT or A16..A21 lines.