The motherboard kit comprises parts to build a Single Board Computer with these main features:

• Z180 CPU running at 18.432 MHz
• 512k byte RAM
• 512k byte Flash containing RomWBW
• 512k byte Flash containing SCM
• Two asynchronous serial ports
• Two 5 volt SPI ports
• One 5 volt I2C bus master port
• Real-time clock
• Voltage supervisor
• Three 80-pin expansion sockets

Optional items:

• Micro SD card adapter
• Serial adapter to USB
• USB cable, A to mini-B, 18"/500mm long
• Adapter cable, 6-way, 8"/200mm

If you are looking for something a little simpler, you might like to consider SC114 or SC130.

RomWBW is a ROM-based operating system for retro computers. It includes CP/M 2.2 and Z-System and supports a wide range of hardware, including SD cards and Compact Flash cards for storage. 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 (SCM) is my own classic machine code monitor. This is provided in the second Flash ROM. Both Flash ROMs can be installed at the same time, but only one can be selected at a time. Selection is with a jumper or external switch.

Expansion is available using the three 80-pin sockets. One is mounted horizontally to allow an extension backplane to be fitted, such as SC113 or SC702.

The optional micro SD card adapter can be connected to one of the SPI ports. RomWBW supports SD cards for CP/M and Z-System file storage. This adapter is not a well behaved SPI device and prevents the use of the second SPI port.

The optional FTDI style serial adapter allows the connection of one of the motherboard's serial ports to a computer running a terminal emulation program. A USB type A to mini-B cable is required between the serial adapter and the USB port of a computer. The motherboard has two serial ports that can be used at the same time, so you may want 2 serial adapters and USB cables.

Both the serial adapter and the micro SD card adapter can be connected directly to the motherboard or can be used remotely using the optional 6-way adapter cable.

The 80-pin expansion slots are RC2014 compatible but extended to 80 pins.

Only one Micro SD adapter can be used as their design, unfortunately, limits them to not sharing an SPI bus.

Whilst the circuit board has a minimum of 2.54mm (0.1") component lead spacing, making soldering relatively easy, it is probably best not to think of this as a beginner's kit. It does, however, have a self-test diagnostic LED port, which can be very useful.

Ordering

The full kit plus optional accessories (cables and adapters) contains everything you need to build a complete working system, except a CR2032 battery, a micro SD card, solder, tools, and cleaning materials.

The ROMs supplied in the component set are programmed with 1/ the Small Computer Monitor and 2/ RomWBW.

You will need a terminal or a computer running a terminal emulation program, such as Tera Term, to communicate with the motherboard.

Documentation

The documentation can be found at www.smallcomputercentral.com

Compatibility

This module conforms to the RCBus specification v1.0, except it was produced before the specification was written and therefore some signals that might be expected, such as INT1 and INT2, are not connected to the bus.

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.

Dimensions

The assembled kit is approximately 10cm (4") x 17cm (7") x 6cm (2.5"). It is typically supplied in a box approximately 23cm (9") x 16cm (6.5") x 2.5cm (1") weighing about 300g (0.7lbs).

The kit

This kit includes all the components needed to make the module, as shown in the first picture, except the CR2032 battery. Other modules and backplanes shown in the pictures are not included. You will require tools, solder, and cleaning materials to assemble this kit.

The Z180 CPU (Z8S180xx) is no longer in production and finding stock is becoming increasingly difficult. The CPU supplied in this kit is either the 20MHz or 33MHz version, and is either old or used stock. I test all of them before packing in kits. Some of the CPUs have superficial scratches.

Printed Circuit Board

The printed circuit board is available on its own here.

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.

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