Maplin ROM Box

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 addresss)
• 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.

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  ROM Box with ROMs

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  ROM Box

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  ROM Box and photocopy of how-to build manual

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  Connected showing ROMs

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  PCB Top (1)

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  PCB Bottom (1)

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  PCB Top (2)

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  PCB Bottom (2)

• Amstrad Expansion System Part 1: Maplin ROM-Box Manual (pdf)
• Amstrad Expansion System Part 2: 6x8bit I/O Port (pdf)

• Info on EURO-card standard
• http://www.maplin.co.uk/