This modular Z80 computer runs RomWBW, which includes a very good implementation of CP/M. It also runs the Small Computer Monitor (SCM).

Both firmware options are included in the kit and can be installed at the same time as the memory module has two sockets for FLASH memory chips. A switch selects which firmware is used.

RomWBW includes CP/M and a range of useful software. It also supports a wide range of add on hardware. RomWBW has been provided free of charge by its author Wayne Warthen. Thank you, Wayne, for providing this and all the support.

The Small Computer Monitor is a capable machine code monitor. The ROM also includes a version of BASIC and a CP/M boot loader (for CP/M installed on a Compact Flash card).

The base computer is formed from the following backplane and modules:

• SC673 - Backplane, 10 vertical sockets, 1 horizontal socket and a 5 volt power input
• SC601 - Z80 CPU module with clock, reset/supervisor and status LEDs
• SC602 - Memory module with 512k bytes RAM, 2 x 512k bytes Flash ROM
• SC610 - Serial module with one 115200 baud serial port
• SC611 - MicroSD card storage module

Recommended accessories:

• SC302 - Serial to USB adapter
• SC305 - Adapter cable, 6-way
• SC306 - USB cable A to mini-B

Also recommended are many of the available RCBus and RC2014 compatible modules. Here are a few to consider:

• SC604 - Compact Flash module
• SC605 - Digital I/O module
• SC606 - Real time clock module

Features

• Z80 processor
• 512k bytes RAM
• 2 x 512k bytes FLASH
• 7.3728 MHz clock
• Status LEDs
• Voltage supervisor and reset
• One asynchronous serial port at 115200 baud
• MicroSD card slot for file storage
• Backplane with power input
• Six expansion slots free for additional modules
• RomWBW in Flash ROM
• Small Computer Monitor in Flash ROM

Documentation

The documentation can be found at www.smallcomputercentral.com

Compatibility

This backplane conforms fully to the RCBus specification v1.0 for 40-pin systems.

The RCBus specification includes RCBus-2014 (both RC2014 standard 40-pin bus and RC2014 enhanced 60-pin bus) and also the full 80-pin RCBus. The 80-pin RCBus provides support for advanced Z80 features, such as the interrupt daisy-chain, as well as support for other processor families.

The Kit

The full kit includes all the components needed to make the modular computer, as shown in the first picture, including mounting screws and spacers. Other modules and backplanes shown in the other pictures are not included. You will require tools, solder, and cleaning materials to assemble this kit.

You will also need to supply a MicroSD card (2GB to 16GB cards are recommended) and a 5-volt power supply (rated at 1 amp or more).

All of the through-hole integrated circuits supplied in this kit are brand new parts from major suppliers, such as Mouser, DigiKey, RS and Farnell, except for the 68B50 ACIA. The 68B50 has been out of production for some time and is not available from these major retailers. It therefore has to be sourced as old stock or as used components, but I do test them.

Printed Circuit Board

The printed circuit board is available on its own here.

Alternative Complete Systems

• SC114 RCBus-40pin Z80 SCM & BASIC Motherboard
• SC126 RCBus-80pin Z180 RomWBW CP/M Motherboard
• SC720 RCBus-80pin Z80 RomWBW CP/M Motherboard
• SC791 RCBus-80pin Z80 RomWBW CP/M Computer
• SC792 RCBus-80pin Z180 RomWBW CP/M Computer
• SC794 RCBus-80pin Z80 RomWBW SCM CP/M Computer
• SC131 Pocket-sized Z180 RomWBW CP/M computer

Notes

• This product is supplied as a kit of parts that require assembly.
• It is your responsibility to pay any import duty or taxes charged by your home country.
• This product is designed for hobby use and is not suitable for industrial, commercial or safety-critical applications.
• RomWBW is copyright Wayne Warthen and has been provided free of charge with his permission.
• RC2014 is a trademark of RFC2795 Ltd.