Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!uw-june!uw-entropy!dataio!paul
From: paul@Data-IO.COM (Paul Brownlow)
Newsgroups: sci.electronics
Subject: Re: I Can't copy an EPROM... Help!
Keywords: EPROMS
Message-ID: <1692@dataio.Data-IO.COM>
Date: 16 Sep 88 18:08:57 GMT
References: <7023@aw.sei.cmu.edu> <4088@louie.udel.EDU>
Reply-To: paul@dataio.Data-IO.COM ()
Organization: Data I/O Corporation; Redmond, WA
Lines: 33

In article <4088@louie.udel.EDU> berryh@udel.EDU (John Berryhill) writes:
 >
 >
 >Have you compared timing diagrams?
 >
 >John Berryhill

The timing diagrams don't always tell the complete story
(or the true story!).  Different manufacturers' EPROMs will
not always act the same, even though the spec sheets
say they should.  One common difference is in the order
of the falling of /OE with respect to /CE.  Some EPROMs will
not output the data if /OE falls before /CE; others
will not function properly if /CE is held low between
address changes.  Some EPROMs will work in all cases.

All EPROMs work if the part is completely disabled between
address changes; i.e. /CE and /OE are high at this time.
/CE must then fall, followed by /OE.  Read the part.
raise /OE, then /CE.  Move to the next address.

In your case, you should probably try to find another
EPROM made by the same manufacturer as the original.  The
programmer is writing the EPROM correctly; it's your
system that can't read it.

Paul

-- 
Paul Brownlow			Data I/O - FutureNet	Redmond, WA
..uw-beaver!uw-entropy!dataio!paul

"It's my snake!  I trained him, I'm gonna eat him!"