The Acorn Plus 1 Expansion module

The Acorn Plus 1 Expansion module added an Analogue port, Printer port and two general purpose expansion sockets to the Acorn Electron. It slotted into place onto the rear expansion connector of the Electron and was fixed in place with two large fixing screws holding the Acorn Electron and Plus 1 together securely.

The Acorn Plus 1 Expansion module

Inside the Acorn Plus 1 Expansion module was an extra ROM socket which provided the extra functions required to control the Analogue and Printer ports and a handful of logic chips to hang it all together. Although the analogue port and printer port were not driven by the same chips as the BBC Micro's implementation, they were programmatically compatible although any software that accessed the printer port required the memory map address at which the printer port live to be changed to suit the Acorn Electrons memory map.

The Acorn Plus 1 Expansion module opened

One of the easiest modifications that could be carried out on the Acorn Plus 1 Expansion was to replace the Acorn Expansion ROM (v1.00) with the Slogger Expansion ROM (v2.02) which contained several useful utilities which provided the ability to map a joystick to key presses for joystick support in games that didn't directly support them and other features such as support for loading and saving ROM images into Sideways RAM.

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