Re: [stella] EPROMs

Subject: Re: [stella] EPROMs
From: Mark De Smet <de-smet@xxxxxxxxxxxxxxx>
Date: Sun, 2 Sep 2001 23:57:36 -0500 (CDT)
> Well, I just got back from the Hamfest in Shelby, North Carolina.. Among
> other things I picked up an EPROM programmer with a 28-pin ZIF socket,
> that can program 2700-series EPROMs. Unfortunately, the guy didn't have
> any EPROMs left, but I did find another guy who had some.
> Now, I freely admit, I don't know the slightest thing about EPROMs, so
> don't laugh if this sounds like a stoopid question, but..
> 2 of the chips I got are labelled `M2732AFI 21V Fast', and appear to be
> brand new. Are these things fully compatible with the standard 2732? I'm
> assuming that EPROMs are like RAM, and will run just fine at a slower
> speed than they are rated, but what about the programming voltage/timings?
> The rest of the chips I got are 27C128's. I assume the C means CMOS. I
> haven't yet found a data sheet for these, but somebody on this list can
> probably give me the short answer: Will these 27C128's (a) work in a
> programmer designed for regular 27xx series, and (b) assuming I get them
> programmed, will they work in a 2600 cartridge? (Yes, I have 74xx inverters)

A Quick tutorial about 27 series eproms.  They are all the same with a few

The numbers that follow 27 show the size in kilo-bits.

If there is a -number after, that indicates the speed, ie 25 is 250ns
This is useually the time between address valid, /CE and /OE = 0V to data
output valid.  250's worked for me, and I doubt you can get something
slower.  Faster shouldn't be a problem.(unless you go to fast)  I've gone
down to 120 w/o a problem

The letter mixed in there can lead you the programming voltage.  If
talking about 2732's, there are generally 3 types, 2732, 2732A and 27C32.  
All three have different programming voltages.  2732 IIRC is 21.x V, 2732A
is 12.5V, and I think 27C32 is also 12.5V, but not sure(I wouldn't tell a
programmer that you have a 2732A if you are using a 27C32 though)

To your questions:  as long as you wire them correctly(data to data, power
to power, OE to OE etc...), there will be no damage to the VCS.  However,
if you use a 2732A in a programmer that is configured for 2732, then you
will most likely destroy the chip(possibly damage to programmer, but I
doubt it)  This is because the programmer will be using a programming
voltage above that rated for the eprom.  Unless your programmer is very
old, it should be able to handle all of the above types, with the
appropriate setting.  Usually via the pc(either through pc program, or
terminal w/ serial link), you choose the chip type.  Find the correct
setting for the chip you are using.  Be sure to match both the 27 series,
the size, and the programming voltage type.  If you match those, you
shouldn't have any problems.  If there are leading letters(which usually
denote a manufacture), try to match those as well, but if you can't it is
ok to try a setting for a different manufacturer.  The only difference
that is likely between manufacturer's is the write timing etc.  If there
is no match, then the programming won't work quite right, but no damage
will be done. 

A quick sample of manufacturer's prefixs:
TMM - toshiba
D   - Intel

Hope that helps,

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