Econet is the local area networking system for BBC Micro computers. To relive our childhoods, we're going to build an Econet at the lab.
Option 1: Aftermarket and fully configurable clock from BeebMaster. £50.
Option 2: Econet hub circuit from Mark Usher, incorporating workstation junction and terminators. Clock duty cycle is fixed at 50%.
Option 3: Build our own clock with an ATtiny and a differential driver IC. Would need to consider the maximum speed at which the ATtiny could maintain a clean clock signal. If we take this option, Tim suggests building it into a hub unit with 4-5 sockets (2 passthrough and 2-3 workstation), but keep the terminators as separate plug-in components.
5-pin Male to 5-pin Male. One is required for each workstation to connect to a junction, and one between each junction.
Tim recommends buying some cheap ready-made cables from ebay (usually sold for audio or MIDI applications). Make sure that the cables have all 5 pins fully-connected.
We can make our own cable if we need to link further than 5M (e.g. across the length of the lab).
We should also consider whether to span between G1 and G8. It should be possible to use the spare CAT5 port next to galahad and patch that into G8.
Tim has a stock of 6-core shielded cable that would be suitable for custom cables.
A passive design, suitable for building into a 5-pin DIN plug, is available:
|2||56R 0.25W resistor|
|1||220R 0.25W resistor|
|2||1K 0.25W resistor|
|1||10uF 16V tantalum capacitor|
We will probably need to purchase 1/4W resistors as most of our stock is 1/2W.
We would require two terminators, and consider making a spare.
Tim has ordered a 5-pack of Econet modules for BBC Master or Archimedes.
We will burn our own ANFS EPROMS.
|3||1K 0.25W 10% resistor|
|3||1M5 0.25W 10% resistor|
|1||1K 0.25W 2% resistor|
|1||1K5 0.25W 2% resistor|
|4||10K 0.25W 2% resistor|
|4||56K 0.25W 2% resistor|
|4||100K 0.25W 10% resistor|
|1||22K x8 resistor pack||Farnell 9356924 £0.31|
|1||2.2nF ceramic capacitor|
|1||10nF ceramic capacitor|
|1||10uF tantalum capacitor 6.3v|
|1||100pF ceramic capacitor|
|1||74LS74||Ordered from Mouser|
|1||74LS132||Ordered from Mouser|
|1||74LS244||Ordered from Mouser|
|1||75159||Ordered from Mouser|
|1||68B54||(obsolete item, ordered from ebay by Al)|
|2||LM319||Ordered from Mouser|
|1||74LS163||Ordered from Mouser|
|1||74LS123||Ordered from Mouser|
|1||2764 EPROM||(will use old EPROM from Hacklab stock)|
|1||5-pin DIN PCB socket||180-degree 5-pin. Appears to be a standard PCB footprint.|
|1||8-way wafer plug||8×2 0.1“ header and jumpers (for selecting ID)|
|7||mini-shunts||(to be identified)|
To show-off our network, we'll want to host some applications.