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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>A basic question about data bus transfer</title><link>https://community.arm.com/developer/tools-software/tools/f/armds-forum/912/a-basic-question-about-data-bus-transfer</link><description> Note: This was originally posted on 29th August 2011 at http://forums.arm.com In AMBA AHB spec2.0 or AHB lite, for the data bus transfer with byte, there is a table (Active byte lanes for a 32-bit little-endian data bus) as shown in the attachment. I</description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: A basic question about data bus transfer</title><link>https://community.arm.com/thread/2685?ContentTypeID=1</link><pubDate>Wed, 11 Sep 2013 11:04:41 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:8616a168-609a-46f3-a8fd-85b6c043fc5b</guid><dc:creator>Colin Campbell</dc:creator><description>&lt;div&gt;&lt;i&gt;Note: This was originally posted on 30th August 2011 at &lt;a href="http://forums.arm.com"&gt;http://forums.arm.com&lt;/a&gt;&lt;/i&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;The AHB (or AHB-lite) HADDR bus states the address of the required transfer. If this transfer is a byte transfer the HADDR value will include the &amp;quot;address offset&amp;quot; that tells you which byte lane is being used. So tables 3-6 and 3-7 in the spec show you the active byte lane(s) for various width transfers for various LSB combinations of HADDR (the offsets).&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;You cannot just attach an 8-bit device to D[7:0] only, it would need a MUX to select the relevant byte of the HWDATA bus, but for reads you could drive all bytes of the HRDATA bus with the same 8-bit read data value, and the AHB master will sample the byte from the correct byte lane it receives.&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;JD&lt;/span&gt;&lt;/div&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: A basic question about data bus transfer</title><link>https://community.arm.com/thread/2684?ContentTypeID=1</link><pubDate>Wed, 11 Sep 2013 11:04:41 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:c44d88f2-e11a-4256-b57f-8a72e8e8f229</guid><dc:creator>Colin Campbell</dc:creator><description>&lt;div&gt;&lt;i&gt;Note: This was originally posted on 5th September 2011 at &lt;a href="http://forums.arm.com"&gt;http://forums.arm.com&lt;/a&gt;&lt;/i&gt;&lt;br /&gt;&lt;br /&gt;&lt;blockquote&gt;&lt;br /&gt;However, I thought it is not a good idea to do this.&lt;br /&gt;&lt;/blockquote&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;Why not ?&lt;/span&gt;&lt;/div&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: A basic question about data bus transfer</title><link>https://community.arm.com/thread/2683?ContentTypeID=1</link><pubDate>Wed, 11 Sep 2013 11:04:41 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:47643360-acc6-4143-a973-e342c8ad6868</guid><dc:creator>Jerry Feng</dc:creator><description>&lt;div&gt;&lt;i&gt;Note: This was originally posted on 3rd September 2011 at &lt;a href="http://forums.arm.com"&gt;http://forums.arm.com&lt;/a&gt;&lt;/i&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;Thank you very much.&lt;/span&gt;&lt;br /&gt;&lt;span&gt;I got it.&lt;/span&gt;&lt;br /&gt;&lt;span&gt;The low bits of HWADDR is used to identify offset.&lt;/span&gt;&lt;br /&gt;&lt;span&gt;Then, if I want to transfer 8 bits in 32 bits bus in write mode, it will change its lane from time to time.&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;However, I thought it is not a good idea to do this.&lt;/span&gt;&lt;/div&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: A basic question about data bus transfer</title><link>https://community.arm.com/thread/2682?ContentTypeID=1</link><pubDate>Wed, 11 Sep 2013 11:04:41 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:35d85e5f-749d-4c6a-b0e7-c5018773900c</guid><dc:creator>Jerry Feng</dc:creator><description>&lt;div&gt;&lt;i&gt;Note: This was originally posted on 29th August 2011 at &lt;a href="http://forums.arm.com"&gt;http://forums.arm.com&lt;/a&gt;&lt;/i&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;Is the question too simple or other else?&lt;/span&gt;&lt;br /&gt;&lt;span&gt;Can anyone tell me why I need to put byte in different lanes if I only need to transfer byte by byte?&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;span&gt;Thank you very much.&lt;/span&gt;&lt;/div&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>