[sebhc] ET-3400 interest?

Timothy Weber 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 

Any thoughts?
Timothy J. Weber
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