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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>problematic douts</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/18450/problematic-douts</link><description> hai, 
iam using 8051 since 2 months. 
iam having some doubts. 
1.how much maximum external memory(ram) i can access through 8051 </description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: problematic douts</title><link>https://community.arm.com/thread/43498?ContentTypeID=1</link><pubDate>Sat, 29 Jan 2005 00:06:27 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:a1d15c5b-2926-4183-a7e7-094ced0a6c16</guid><dc:creator>Neil Kurzman</dc:creator><description>&lt;p&gt;The simple answer is 64K for a plain 8051.&lt;br /&gt;
More is you want to do banking.&lt;br /&gt;
More for some variants.&lt;br /&gt;
lees or none for other varients.&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: problematic douts</title><link>https://community.arm.com/thread/96896?ContentTypeID=1</link><pubDate>Fri, 28 Jan 2005 04:27:19 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:1be8e6de-fbc8-415a-adbf-35cd97816599</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;i&gt;&amp;quot;Using xdata banking you may &lt;b&gt;extend&lt;/b&gt; the address space...&amp;quot;&lt;/i&gt; (my emphasis)&lt;br /&gt;
&lt;br /&gt;
For any processor, the amount of memory addressable is governed by the width of the databus (which is usually closely related to the processor&amp;#39;s Word size).&lt;br /&gt;
This information can be found in the &lt;b&gt;Datasheet&lt;/b&gt; for the specific device.&lt;br /&gt;
Note that not all 8051 derivatives today provide an external memory interface - so they&amp;#39;re further limited to what&amp;#39;s on the chip.&lt;br /&gt;
&lt;br /&gt;
You can, of course, expand the addressing range of any processor with suitable hardware and software; eg, Keil&amp;#39;s &lt;b&gt;XDATA Banking&lt;/b&gt; for the 8051, or the disk-based &lt;b&gt;Virtual Memory&lt;/b&gt; found on big systems.&lt;br /&gt;
&lt;br /&gt;
So the question &lt;i&gt;&amp;quot;how much maximum external memory(ram) i can access?&amp;quot;&lt;/i&gt; is really just another &lt;i&gt;&amp;quot;how long is a piece of string?&amp;quot;&lt;/i&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: problematic douts</title><link>https://community.arm.com/thread/87086?ContentTypeID=1</link><pubDate>Fri, 28 Jan 2005 01:09:23 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:e493a569-a8ab-4650-a008-c7d3c3dc0f5c</guid><dc:creator>Keil Software Support Intl.</dc:creator><description>&lt;p&gt;Using xdata banking you may extend the address space up to 2 MB.&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: problematic douts</title><link>https://community.arm.com/thread/43488?ContentTypeID=1</link><pubDate>Wed, 26 Jan 2005 09:20:37 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:34e83744-e69f-42ba-94c9-a56387db9f30</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;You need to start with the basics: read the followig documents - commonly referred to as &amp;quot;the bible&amp;quot; for the 8051:&lt;br /&gt;
&lt;br /&gt;
Chapter 1 - 80C51 Family Architecture:&lt;br /&gt;
&lt;a href="http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_ARCH_1.pdf" target="_blank"&gt;http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_ARCH_1.pdf&lt;/a&gt;&lt;br /&gt;
&lt;br /&gt;
Chapter 2 - 80C51 Family Programmer&amp;#39;s Guide and Instruction Set:&lt;br /&gt;
&lt;a href="http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_PROG_GUIDE_1.pdf" target="_blank"&gt;http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_PROG_GUIDE_1.pdf&lt;/a&gt;&lt;br /&gt;
&lt;br /&gt;
Chapter 3 - 80C51 Family Hardware Description:&lt;br /&gt;
&lt;a href="http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_HARDWARE_1.pdf" target="_blank"&gt;http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_HARDWARE_1.pdf&lt;/a&gt;&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>