The later cardWith reference to the early card, the Econet module expansion card is a very good idea.
Although one could argue that the retail price was a little steep and amusingly varied...
£42 from Watford, £43 from College Computers, £46 from Dabhand and Desktop Projects, £48 from Orion Computers, £49 from Morley....one thing is for certain, whip the lid off your A3000, plug in an Econet card, put the lid back on. As soon as you power up, you'll be all network ready. It is also worth remembering that not only was Ethernet (10mbit) not available for the 6502 machines, but in those days a RISC OS podule would give you little change from £260 (with VAT).
The interface card, the ADF10, contains collision detection circuitry to help make the network more reliable and faster to use. This is working upon the logic of "why implement something in software that can be done quite easily in hardware?", rather like accelerated graphics cards in modern computers - the objective is to free the processor from having to do pointless tasks.
The interface itself consists of a small PCB upon which is mounted a 68B54 ADLC and its support circuitry. The long row of pins (bottom right of picture below) is an 8-bit data bus to the host computer, along with various control signals and power. The second row of five pins (upper right, beside that yellow capacitor) connects to the Econet socket in the back of the computer. Because of the larger component count, the later cards are maginally bigger.
These cards were able to be used interchangably in:
Here is a scan of an later style network card. I apologise for the blurriness, however my scanner has extremely precise focusing...