[sebhc] ET-3400 interest?
tw at timothyweber.org
Fri Jan 6 11:13:00 CST 2006
davidwallace2000 at comcast.net wrote:
> Yeesh! I remember that beast. I borrowed one for a week when I went on vacation one year. (It was something to play with because I couldn't take my H8.) I forget exactly what I programmed it to do, but it was my first and only attempt to write code in 6800 machine language.
It was certainly not the introductory programming experience I'd
recommend to a novice now... though it certainly started me off with a
good understanding of the hardware!
Paul A. Pennington wrote:
> Me three...
> I'd like jangle some very old brain cells by writing a little 6800
> machine code and doing some projects on my ET-3400. Those with Motorola
> Evaluation Kits (D-1 or D-2) might join in also, with modifications for
> different I/O.
What are those?
William Wilkinson wrote:
> My ET-3400 has been gathering dust for years. It would be interesting to
> get it going again and see what I could make it do with its fully-loaded
> 512 bytes of RAM.
I'm trying to talk myself out of the impulse to build a whole new
machine around it - could easily add a serial port, A/D, etc., but it
seems to push the limits of utility! - and instead focus on just adding
persistent storage. Though the sheer perversity of expanding its
capabilities might be fun too.
So my current plan is to use an Atmel 8K EEPROM, which was just the
smallest parallel EEPROM I happened to find quickly. I've got the
address decoder set up and working to pull a line low when any address
in the 0x8000 range is on the bus, and I think all that remains is to
get the chip, plug it into the lower 13 address lines and data bus, hook
its enable line to the decoder's output, and connect its R/W line.
Then I expect to just be able to write bytes into the EEPROM at that
address block using the monitor ROM. I'll probably write one "Copy
block" routine, to input a start, end, and destination address, and copy
the bytes over, waiting for the EEPROM to finish writing where
necessary. Reading should "just work."
Once that's in, it should be easy to put new code anywhere in that
(gargantuan!) 8K address space, using the lower 512 KB as a scratchpad.
Or, for the realistic feel, I could run a routine out of the EEPROM
that would copy the "real" program down into RAM first, just so I could
say it was really running on the old hardware and only using the modern
stuff for persistence.
Adding a serial port so I could write in C on a PC, compile, assemble,
link, and download the object code to the EEPROM seems... cool but
Timothy J. Weber
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