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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>AT 89c51ED2  psen pin is always low</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/24075/at-89c51ed2-psen-pin-is-always-low</link><description> 
Well Iam successfully able to load my program to AT89C51 IC howevr
iam not able to retrive the data. 
When I checked the PSEN pin the its low even after programming the
flash insideis not transmittinmg and data... 
KINDLY help.... 
 </description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: AT 89c51ED2  psen pin is always low</title><link>https://community.arm.com/thread/114123?ContentTypeID=1</link><pubDate>Tue, 22 Jul 2008 09:12:15 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:8e3fd238-d543-450b-8e8c-c963f9314cda</guid><dc:creator>abel gaius</dc:creator><description>&lt;p&gt;&lt;p&gt;
Martin Thank u for the reply , but can u PLS explain in detail
using a schematic of AT89C51ED2 chip.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AT 89c51ED2  psen pin is always low</title><link>https://community.arm.com/thread/100917?ContentTypeID=1</link><pubDate>Sun, 20 Jul 2008 13:49:33 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:c56dc638-afe4-442c-b4d5-edf132782b35</guid><dc:creator>Martin Persich</dc:creator><description>&lt;p&gt;&lt;p&gt;
If you cant&amp;#39;t connet to AT89C51ED2 bootloader with FLIP, the
problem may be with PSEN condition during &amp;quot;reset&amp;quot;. On some MCU
(abbout 10 % of MCU&amp;#39;s) must be strictly observed PSEN condition
during &amp;quot;reset&amp;quot;. I quote datasheet: &amp;quot;The Hardware conditions (EA = 1,
PSEN = 0) during the Reset# falling edge force the on-chip bootloader
execution. &lt;b&gt;As PSEN is a an output port in normal operating mode
after reset, user application should take care to release PSEN after
falling edge of reset signal. The hardware conditions are sampled at
reset signal falling edge, thus they can be released at any time when
reset input is low.&lt;/b&gt; &amp;quot;. I have special &amp;quot;add-om&amp;quot; hardware unit to
start bootloader on some MCU ...&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AT 89c51ED2  psen pin is always low</title><link>https://community.arm.com/thread/76508?ContentTypeID=1</link><pubDate>Sat, 19 Jul 2008 09:13:18 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:6c68b813-37bc-4955-9146-3ca934b701c9</guid><dc:creator>abel gaius</dc:creator><description>&lt;p&gt;&lt;p&gt;
yes iaam not abel to get the dat stored in internal flash in the
AT89C51ed2 IC&lt;/p&gt;

&lt;p&gt;
I need Hardware design guide lines like filter capacitors on 89c51
ed2 .. what should be its value..&lt;/p&gt;

&lt;p&gt;
i have lost many of my m,icrocontrollers for the same reason ..
its programmong but the dat iam not able to retrieve... Kindly give
me HARDWARE spec regarding the same&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AT 89c51ED2  psen pin is always low</title><link>https://community.arm.com/thread/52058?ContentTypeID=1</link><pubDate>Sat, 19 Jul 2008 00:32:44 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:26d9a9dd-2ca1-4ff8-b2f7-b4ccdcc5371c</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;p&gt;
What data?&lt;/p&gt;

&lt;p&gt;
Are you trying to read back the code that you programmed?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>