A later design is now available: SC721

This product is designed to work with a Z180 CPU module, such as SC111.

This module contains two 512k byte Flash ROM chips and one 512k byte RAM chip. Only one of the Flash ROM chips can be mapped into memory at any given time.

A jumper, or external switch, selects which of the Flash ROM chips is used. Alternatively, an external control signal could be connected to the switch header and used to control selection. By this method, it would be possible to access all 1024k bytes of Flash memory.

The memory is organised in a 1M byte linear memory space. In order for a Z80 family CPU to access 1M byte of memory, some form of memory management (eg. paging) is required. As this module does not include such a feature, memory management must be provided elsewhere. The Z180 CPU includes suitable memory management, but the standard Z80 CPU does not.

In order to support the extra address lines needed for 1M byte of memory, a suitable backplane is required, such as SC112 or SC701.

The Flash memory supports being written to by the CPU, thus allowing the firmware to be updated, or “Flashed”. This is unlikely to happen by accident due to the software requirements for writing to the Flash, but to play safe each Flash chip has a jumper to select hardware write protection.

Documentation

The documentation can be found at www.scc.me.uk or by following the link below.

Compatibility

This module conforms to the RCBus specification v1.0, except it was produced before the specification was written and therefore is does not follow all the suggestions for this type of module, such as being able to select ROM at the top of memory to support other processor families.

The printed circuit board outline conforms to the RC2014 standard for full height modules.

This module requires an 80-pin backplane, such as SC112 or SC701, and a suitable CPU module, such as SC111. RC2014 backplanes are not suitable as they do not have the required extra pins.

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

Two Flash chips are included in the kit. One contains RomWBW (configuration RCZ180_nat), while the other contains the Small Computer Monitor (configuration S5).

The kit contains everything you need to build the memory module, except solder, tools and cleaning materials. To use the completed module you require a suitable Z180 CPU module, a suitable backplane, a USB to serial adapter (5-volt power and 5-volt signals), a computer, and a terminal program (such as Tera Term).

Printed Circuit Board

The printed circuit board is available on its own here.

Notes

• This product is supplied as a kit of parts which require assembly.
• It is your responsibility to pay any import duty or taxes charged by your home country.
• My products are made in accordance with the "designed for RC2014" labelling scheme.
• RC2014 is a trademark of RFC2795 Ltd.
• This product is designed for hobby use and is not suitable for industrial, commercial or safety-critical applications.
• RomWBW is copyright Wayne Warthen and is supplied with his permission (at no extra charge).