We’ll now look at how to make a diode: in other words, how to allow electrons to flow only one way along a wire.
It’s worth noting that we don’t actually use the diode much in practice, as it is very rare for a wire to be used to communicate in both directions; however, it’s instructive to look at and lets us review the rules of Wireworld.
The picture shows two wires. The upper one has a diode facing forwards, while the lower one has a diode facing backwards. As you can see, the diode blocks electrons flowing in the opposite direction to the way it is facing.
How does it work?
Recall from the rules that a copper cell becomes an electron head if it has just one or two neighbours that are electron heads. If three neighbours are electron heads, the cell will remain copper. This is the key to the operation of the diode. As an electron attempts to flow through the diode, there comes a point (generation number 1 in this case) when a column of three cells simultaneously become electron heads. In the top case in the picture above, the electron heads can propagate to the next column to the right, as each copper cell in that column is only adjacent to two of the heads. In the bottom case, however, the copper cell in the next column is adjacent to three heads, and so the flow stops.
Next we shall look at how to perform logical operations on Wireworld signals.
This page most recently updated Thu May 28 13:58:55 BST 2015
Qxw is a free (GPL) crossword construction program. Answer treatments, circular and hex grids, jumbled entries, more besides. Release 20140331 for both Linux and Windows. More...
My book, ‘Practical Signal Processing’, is published by Cambridge University Press. You can order it directly from them, or via amazon.co.uk or amazon.com. Paperback edition now also available. Browse before you buy at Google Books. Wydanie polskie.
If you find this site useful or diverting, please consider a donation to NASS (a UK registered charity), to KickAS (in the US), or to a similar body in your own country.
All trademarks used are hereby acknowledged.