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.
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.
| Reference | Description | Comment |
|---|---|---|
| J1 | 2x25 pin header, 2.54 mm, right angle | Plugs into Zeal 8-bit backplane |
| J2 | 2x40 or 1x40 pin socket, 2.54mm, right angle | Socket for RCBus board to plug into |
| JP1, JP2, JP3, JP4 | 2-pin header | A7-A4 invert jumpers |
| U1 | 74HCT86 (DIP-14), with optional socket | Quad 2-input XOR gate |
| C1 | 0.1µF ceramic capacitor | |
| JP5 | 2-pin header, 2.54mm | (optional) Disable Zeal 8-bit on-board ROM |
| J3 | 2-pin header, 2.54mm | (optional) RX/TX pins of RCBus |
- Gerber files are in production directory (JLCPCB, PCBWay, etc.)
- Read-to-order PCB at PCBWay
- Schematics in PDF format: zeal8bit-rcbus.pdf
- KiCad 9.0 project in this directory
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.
Use the online configuration tool to determine which address lines (A7-A4) need inversion for your specific RCBus board. Set jumpers JP1-JP4 accordingly.
Licensed under CERN-OHL-P v2.
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