Maplin ROM Box
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Contents
Description
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)
Technical
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.
Pictures
ROM Box with ROMs
ROM Box
ROM Box and photocopy of how-to build manual
Connected showing ROMs
PCB Top (1)
PCB Bottom (1)
PCB Top (2)
PCB Bottom (2)
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Manual
- Amstrad Expansion System Part 1: Maplin ROM-Box Manual (pdf)
- Amstrad Expansion System Part 2: 6x8bit I/O Port (pdf)
