SC720 is a Single Board Computer (SBC) meaning it can work without any other backplanes or modules. It is based on a Z80 CPU running at 7.3728 MHz, with 512k bytes of RAM, two 512k byte FLASH ROMs, a Z80 SIO/2 providing two serial ports, a Compact Flash card interface, a clean reset, a voltage supervisor, and an output port with eight LEDs. It is powered from an 8 to 15 volt supply at up to 1 amp.

The kit includes RomWBW pre-programmed into a FLASH ROM. This includes CP/M and a range of other software.

The kit also includes the Small Computer Monitor pre-programmed into a FLASH ROM. This includes a capable debug/monitor, BASIC, and a CP/M loader.

Features:

• Z80 CPU running at 7.3728 MHz
• 512k bytes of RAM
• 512k bytes of Flash ROM containing RomWBW
• 512k bytes of Flash ROM containing SCM
• Switch to select which Flash ROM to use
• Two asynchronous serial ports
• Voltage supervisor and reset device
• Three 80-pin RCBus expansion sockets
• Eight LEDs for general status and diagnostic display
• Three LEDs for power, reset and Compact Flash activity

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 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 switch.

Expansion is available using the three 80-pin RCBus sockets. One is mounted horizontally to allow an extension backplane to be fitted, such as SC702, SC710 or SC113.

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.

Documentation

The documentation can be found at www.smallcomputercentral.com

Compatibility

This motherboard conforms to the RCBus specification v1.0 for RCBus-2014 and RCBus-Z80.

Most RCBus, RC2014 and compatible modules can be used to expand this motherboard.

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

This kit includes all the components needed to make the motherboard, as shown in the first picture. Other modules and backplanes shown in the pictures are not included. You will require tools, solder, and cleaning materials to assemble this kit. You will also need a power source (8 to 15 volts). A Compact Flash card is highly desirable to make full use of the kit's capabilities.

All the integrated circuits in this kit are brand new parts from major distributors in the UK or USA.

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.
• The product contains small parts and is not suitable for young children.
• The Compact Flash interface circuit has been designed by Tadeusz Pycio and reproduced with his permission.
• RomWBW is copyright Wayne Warthen and has been provided free of charge with his permission.

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