#EPROM / Cable adaptor
5 messages in this thread
Larry, for some reason or other you just never got back to me after that first
exchange of messages. Whatever. Anyway, I've been busy lately and wnted to
let you kow that the art work for the EPROM adaptor I mentionned to you is now
at my photographers, and I should have my first run of boards by the end of the
month.
These adaptors will allow use of a 27C64 or 27C256 in the M100 expansion
slot, and will support the 27C256 used EITHER as a full 32K chip or as a
emulator for 4 8K by 8 chips via add on switches and proper setting of jumpers.
It also will allow reprogramming of an EPROM that is already soldered to the
adpator board, tho it is designed for use by folks who will first program the
EPROM then solder it to the adaptor. Let me know if you still are interested.
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85605
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I am still interested. Speaking of EPROMs; the reason I haven't been back to
you is because I have been busy with the design of a gang programmer for EPROMs
which we've been doing over the past few months. Just got a number of fixes
designed for an older version and will now design a new model using latest
technology.
Please, if I ever "disappear" after an exchange of messages like that,
don't interpret it as a loss of interest. I have so much to take care of all
the time that it is not unusual for me to become so involved with a particular
project that I simply cannot pull away for anything else unless I skip the 4
hours of sleep I have been getting lately, and if I do that I am useless, as
you can imagine. I wil always show up again ready to pick up where we left
off.
As soon as you have something together let me know. Til then we can of
course continue to discuss the project. The main concern is to find enough ROM
based software to make ROM banks and large ROMs viable, don't you agree?
Larry
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No problem about the disappearance… tho Imust admit that not knowing you
well, I did entertain the notion that you simply lost interest. Tho you seemed
like too nice a fellow to not have simply said that if it were the case. I'll
get back to you when I have some actual working piece of hardware to show you.
As for "Wroking ROM based software", I pointed out that a fair amount of
stuff can simply be ported to the ROM.
Working on an EPROM programmer, eh? Do you properly impliment the fast
algorithm, including pulling Vcc up to 6VDC during programming??? Eh? Many
folks who claim to impliment the fast algorithm don't bother to put in the
extra regulator or the extra switching circuitry. I even saw one fool who just
did a 2ms pass and if it verified he left it at that. And he sold HUNDREDs of
CoCo EPROM programmers. I ended up rewriting his software driver to fix it.
I never did any work on a gang programmer, tho. With 64K CoCo 's available
for under $70, if I needed to burn a lot of EPROMs I'd use my three Color
Computer EPROM programmers and three of my CoCo's!
Be sure you have 12.5 volts for Vpp! in the 2764, 27128, and 27256
category, there are versions that take 21 volts and versions (usually, but not
always, designated by the suffix -A) that take 12.5 vols Vpp. It gets very
confusing! a Fairchild 27C256 reqires 21 V Vpp, and an Intel 27256 takes 12.5
volts.
more later.
—Marty
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85761
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n
Yeah, I know about all the variations in programming. In fact, we were called
in because the original designer did not do the job right, then came down with
cancer; it was a real mess. Since our units compete with the likes of DATA I/O
they must be absolutely perfect. INTEL is qualifying us now which is the acid
test. Our programmer sells for about $2500 so you can imagine the complexity
of the task. 27256 is the weirdo, though. The rest are no trouble.
I will try to keep in touch. I am going on vacation next week and have
promised not to do ANY work or log on here; I really need the break and my wife
and kids deserve a few days of my undivided attention. I will try to get
someone to check in here a couple of times while I am gone.
Larry
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85836
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Funny you should feel the 27256 is such a problem… tho it sure seems you
should know. It took me about a half hour to modify the software and hardware
of my color computer based ERPOM burners for the 27256. True, you have one
less control line (*prog is gone) but the OE line pretty much functions as a
Vpp line in programming mode.
In any case, for $2500 you BETTER have done it right!! There are hacker
one at a time programmers for $300 for the IBM that alledgedly do proper fast
programming of u to 27512's (ever see a spec sheet on a 27512?? I haven't).
My coco burner cost me $20, but then I had to hack on it considerably to make
it useful to me.
Don't get me wrong.. I understand that a lot of work has to go into a GANG
programer that must RIGIDLY meet manufacturers programming specs! I am WELL
aware that just getting the EPROM to READ and Verify is NOT the measure of a
well designed programmer!!! Ya gotta chuck enough electrons into those
fermented farads in that sucker so that it STAYS programmed!!
I just got the photograpy back on that adaptor.. and anticipate first test
of the board in a week or two.
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