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Article #11072

#11072

From: Mr M J Brown
Date: Fri, 06 Nov 1992 13:25

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Date: Fri, 6 Nov 1992 10:41:17 GMT
From: Mr M J Brown <cstadbg@csv.warwick.ac.uk>
Received: by clover.csv.warwick.ac.uk
	id AA19945; Fri, 6 Nov 1992 10:41:17 GMT
To: sdmw91tw@ap08.rz.tu-harburg.de
Subject: Re: Eproms
Newsgroups: sci.electronics
In-Reply-To: <2023@rztsun.rz.tu-harburg.de>
Organization: Computing Services, University of Warwick, UK

In article <2023@rztsun.rz.tu-harburg.de> you write:
>
>I have a little problem with megabit-EPROMs:
>
>Are there any differences between 27c010-120 and 27c020-150 other than:
>
>I was trying to replace the 1Mbit Eproms with 2Mbit, but the system does not
>recognize the chips at all. At least, when I am trying to read from the 
>2Mbit Eprom the system acts as if there was no chip at all.
>

>What is the problem?
>
>

The problem could be that the extra address line that the 2 Meg eprom has
is not connected anywhere in the device you are plugging it into, or it is
tied off to the wrong voltage rail. If your Programmer programs the lower
half of the chip (High Address line = Logic 0 ) and that pin is tied to
+5v (Logic 1) in the application circuit, then you have exactly what you
describe .... the circuit is trying to run with a blank eprom in it!

You could modify the equipment so that the highest address line is tied to
0v ... but make sure you get it right!

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    _/_/  _/_/   _/   _/_/     _/          |         Michael Brown
   _/  _/  _/   _/   _/       _/_/         |
  _/      _/   _/   _/_/     _/            |   cstadbg@csv.warwick.ac.uk
 _/      _/   _/   _/  _/   _/_/_/_/  _/   |
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References: <1992Nov4.155302.24319@newstand.syr.edu> <1992Nov6.124621.8784@bernina.ethz.ch>

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Path: arc1-ca.pugleaf.net!sparky!uunet!pipex!warwick!warwick!not-for-mail
From: cstadbg@csv.warwick.ac.uk (Mr M J Brown)
Newsgroups: sci.electronics,comp.robotics
Subject: sdmw91tw@ap08.rz.tu-harburg.de
Date: 6 Nov 1992 13:25:39 -0000
Organization: Computing Services, University of Warwick, UK
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References: <1992Nov4.155302.24319@newstand.syr.edu> <1992Nov6.124621.8784@bernina.ethz.ch>
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