Maplin ROM Box

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Amstrad Expansion System


The Amstrad Expansion System aka Maplin ROM Card from Maplin is a DIY project by Dave Goodman and John Attfield.

The Amstrad Expansion System (Part 1) is primarily a rom box for the CPC series, but had additional features:

  • Special non-standard Buffered Expansion Port (with pre-decoded IOSEL line, on access to "free" I/O address)
  • Lightpen socket (3.5mm stereo socket - just a connector with LPEN,5V,GND - without any additional electronics)

The Amstrad Expansion System (Part 2) adds some more features:

  • 6x8bit I/O port (using two 8255 PPI chips)
  • Additional power-supply module (PSU)


ROM is selected using an I/O port decoded with A15=1, A13=0. The ROM number is decoded using D3-D0 only, meaning a maximum of 16 ROMs can be used, but the PCB only has 8 sockets available. In addition more then one value can select the same ROM.




"Electronics - The Maplin Magazine" Dec 1985-Nov 1986. Published by Maplin Electronic Supplies Ltd. Page 12 - 18; Video Digitiser. This DIY Kit could be assembled for use in the Buffered Eurocard Extension board of the Maplin ROM Box for use with Amstrad CPC and Z80 Computers. Gives full instructions on how to build it with board layout and list of components.