Ok, here it is. The T2A2. What sounds like a robot from StarWars is actually a Transputer to Apple II interface. Its design is pretty much the same than its cousin, the T2C64, with the addition of some buffers to behave like a good citizen of the Apple-II bus. So this is how the little beast looks as of now (v0.5):
To use the Apple-II bus-connector of the 8Bit-Baby (another brainchild of mine), I had to shuffle the parts around a bit. On top you’ll see the same TRAM used on the T2C64… 20MHz T800 Transputer, 128KB SRAM. Right below it is an LS245 octal bus-transciever to handle signals like DevSel, R/W and A0-3. To its right its the IMS012 Linkadapter converting 8bit parallel bus into INMOS’ serial link-protocol. Below that, there’s the silver 5MHz oscillator to clock the IMS012 as well as the Transputer and another 245 to buffer the data-lines (D0-7). Finally on the left bottom there’s the CPLD which handles the Analyze, Reset and Error lines of the Tranputer as well as chipselect and such (Thanks to Mike for helping out on VHDL here!).
The picture above is the first Prototype and it’s finally working… even it’s a nightmare to look at its back side 😀
But because I’m a Commodore guy who wasn’t able to afford an Apple II in its hey-days I had to start from scratch and learn a lot…
That said, when I finally could afford an Apple II system, I went straight for the IIgs. I think IIgs is the perfect platform for an 8-bit Transputer interface given the amount of available/adressable RAM, native access to harddisks and a decent screen resolution.
Because of its simple design, the T2A2 should also work in any Apple-IIe etc. There’s no ‘firmware’, no EPROM. Just plain simple reading and writing to some (slot)specific addresses.
Due to its close relationship to the T2C64, programming is quite similiar. As a matter of fact I just slightly changed the examples I’ve used on the C64… which is the beauty of the idea.
So jump to the next post to see the first little test proggie in AppleSoft BASIC…