The Electron Interface

By Will Watts

Originally published in EUG #01

As most people know, the Electron's architecture is based on that of the BBC Micro. Back in the early Eighties, the Beeb was the 'Amiga' of its day and most people with an interest in computing aspired to own one, but with a price tag of almost £400, this was just a dream for most. Enter the Electron, which some people have described as the machine that put the power of the BBC Micro within most people's grasp. Others have commented that you only get what you pay for and that the Elk, which cost £199 when first released, is a BBC with all the best bits removed.

One of the attractive features of the BBC was that it came ready to 'communicate' with the outside world. If you look at the back and underside of a BBC you will find the following - a 1MHz Bus, disk drive connector, printer port, user port, RS423 socket and analogue connector as well as a socket to connect a cassette recorder, an auxiliary power output, an Econet connector socket and the 'Tube' which allows the Beeb to 'speak' to a second processor or computer system running in parallel.

Now let's look at the back of an unexpanded Electron. You should see a recess, two round holes on either side and a sheath of plastic covering what is known as a 50-way edge connector. (If your plastic cover is missing, take great care not to damage the exposed gold plated strips!) The edge connector was designed to take Acorn's own interface, the Plus 1, but long before this device went on sale enterprising third party companies got in on the act. First Byte produced a highly successful 'switched' joystick interface, Sign Point brought out a printer port, Mushroom released a combined printer and user port interface and many other companies churned out a stream of weird and wonderful add-ons.

When the Acorn Plus 1 Interface finally became available, those who had ordered one received a plastic box measuring approximately 13.5" x 3.5" x 2" with the same mottled cream finish as the Electron itself. A protrusion on the front of the Plus 1 housed the edge connector socket which slid into the recess at the back of the Electron and the two were firmly locked together using a pair of bolts which came as part of the Plus 1. (Why does the above passage conjure up an image of two stray dogs...?)

Your upgraded Electron was now fitted with two ROM cartridge ports, a parallel printer port and an analogue interface. Most people now refer to the analogue interface as the joystick port but it can be put to other uses. If a Plus 1 is fitted to your Electron and you type *HELP (RETURN) the following message should appear on screen:

   Expansion 1.00 ADC/Printer/RS423

This is an erroneous report as the Plus 1 has no RS423 - which is 'Serial' (as opposed to a 'Parallel') interface. Acorn had intended to include an RS423 in the Plus 1 but later changed their minds. Unfortunately, no-one told the person who wrote the ROM software about this U-turn and so the message stayed.

The printer port allowed the fitting (via a suitable ribbon cable) of any Epson compatible parallel printer. With an Acornsoft View word processing ROM cartridge inserted into either of the Plus 1's cartridge ports, Electron-owners could now manipulate and print out text to their heart's content! (Rumour has it that the manuscripts for several books were produced in this way!)

The third party producers also saw a lot of potential in the cartridge ports and a new generation of add-ons appeared. It really looked as if the Electron was going somewhere...for a while. But then Acorn seemed to lose interest in the Electron and everything to do with it. The bubble had burst.

All was not lost though! Those dedicated third party chappies came to the rescue and these days, companies such as ACP/Pres and Slogger offer more support and free advice than Acorn Computers ever did, and a new 'bubble' has been blown!

Will Watts, EUG #1