Re: EPROM manufacturer and device IDs

[Ludis Langens <ludis@cruzers.com>]

thergen@svn.net wrote:
> 
> "Two idenifier bytes may then be sequenced from the device
> outputs by toggling addrress line A0 from Vil to Vih.  Byte 0 represents
> the manufacturer code and byte 1 , the device identifier code."
> 
> I'm not sure how much commonality there is among the manufacturers on the
> use of this method.

This is quite common.  Expect all current EPROM designs to have this
feature.  However, older devices don't have it.  This means that many of
the PROMs pulled from ECMs don't have the id feature.

My problem is that my new PROM programmer knows all about these ids. 
However, it doesn't want to share this information.  For example, lets
say I've got it set to "National 27C256" and the id checking is turned
on.  I grab the next MEMCAL, plug it in, and tell the programmer to read
the chip.  If the EPROM actually is a National 27C256, it reads it just
fine and I can proceed to saving the data.  However, lets say it is
something else.  The programmer will abort the read saying something
like: "Device Id mismatch, actual id is '8986'."  It doesn't tell me
that 8986 is an Intel 27C256.  It also doesn't automatically switch to
Intel mode and procede.

Not having a big list of these id numbers means that I either have to
turn the checking off, or start guessing from the many possible
manufacturers/devices.  I had a chip which I was 99% certain was a
National 27256 like EPROM.  The programmer rejected it as a National
27C256, 27256, and as an A suffix variant.  It turned out to be a
Fairchild 27C256.  Fairchild was owned by National for a long time, thus
my original hunch was still correct.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/

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