Needham SA-20 Eprom Programmer
Needham SA-20 Eprom Programmer
Attempting File Transfer to SA-20 Using Serial Cable
Having been glad at just getting the SA-20 working with the serial cable, I
was *really* anxious to see if the same file I had tried to transfer to it
with the parallel cable (and failed due to missing bytes) could be able to
transfer successfully using the serial cable. So put in 2716 eprom,
selected device, read chip, set file pointers, transferred to the computer.
Not bad so far, but a little slow at 9600 bps. Verified the checksum was
34511 and matched the checksum of the eprom on the programmer -- all looked
good.
Now for the real test. Transferring back from the PC to the SA-20.
Set the SA-20 to "Receive File" and it transferred & no
on-screen File I/O error message on the programmer like I was getting before!
Checked the checksum of the data in the memory buffer and it was 34511.
AWESOME!!!
I then played around with the baud rate a little more and set the rate to
115.2k in the software and now file transfers & navigating around on the
menus work as fast as they did with the parallel port!
Final Thoughts & Words of Wisdom
First and foremost, if you are one of the few people actually using a
programmer this old and have problems with the parallel cable, try an RS232
null modem serial cable. This goes for any eprom programmer really -- if
it has an RS232 connection and you see some bytes are getting screwed up with
parallel cable, it's worth a shot to try the RS232. Just be sure it has
the correct standard pinout for a null modem cable for your programmer.
I'd be interested in hearing if anyone else had similar issues with parallel
ports and older devices.
Next.. words of wisdom I guess, if you're at all like me and have a hard
time giving up on something -- it can be really *really* annoying to invest
20+ hours into something and still not have it working. So you have to
know when it's just not worth it. But that's a fine line cause it's hard
sometimes if you like learning and figuring things out... somehow you drag
yourself back into the pain :) When you stick with it though and are
successful in the end, it's a great feeling of accomplishment and you most
likely learned a ton. I know this eprom programmer is old and I should
be buying a new one -- and I will buy a new one soon enough since it will
support many more chips, but why buy a new programmer that is spotty with
being able to program these older eproms instead of using something that was
designed to program them reliably in the first place?
Do I recommend you buy any really old programmer and go through the same
frustrating pain I did trying to get it to work? No -- not by any means,
it's a pot luck chance that an old programmer running DOS software is going to
work on a newer machine. But if you buy a Willem programmer, True USB
GQ-4X or a newer USB programmer and you can't program older chips, then look
for an older programmer that supports those chips reliably & that other
people have had luck getting to work on newer computers. I do plan to
buy a newer programmer soon, most likely a GQ-4X, but this old tried &
true SA-20 will be my workhorse for the older chips that I can't program on
the newer programmers, and that's indispensible. Why throw away a chip
thinking it doesn't work when there's a chance it's actually a good eprom
& it's the eprom programmer at fault?
Anyway, I hope the few other people with an SA-10 or SA-20 can save
themselves a ton of aggrivation by finding this article and also be assured
that *someone* has gotten old DOS software written in 1990 to work under
Windows XP on a 1.66ghz Core2 Duo processor using a serial cable. Now
that it's fully working, I really like the SA-20! It's pretty easy to
use and being able to navigate the screens in a DOS window versus on the
programmer itself makes typing in filenames or navigating some of the menus
much faster.
Good luck and happy programming!