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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>seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/26373/sen-urity-bit-in-at91sam7s</link><description> 
Hi, i have a question about an access restriction of writing to
on-chip flash after setting the security bit. Can i program the flash
through an EFC after setting the security bit? 
 </description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/thread/115345?ContentTypeID=1</link><pubDate>Wed, 28 Oct 2009 08:12:11 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:cf58d350-f87a-4a66-a523-bc2221534405</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;A JTAG interface that is allowed to download program code to
RAM, can download a little application that reads out all flash
contents.&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
In case of the AT91SAM7S, the security bit blocks all external
accesses to flash (read + write) except for a full chip erase (which
will also reset the security bit after the erase operation
finishes).&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/thread/103570?ContentTypeID=1</link><pubDate>Wed, 28 Oct 2009 08:03:28 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:8fa34113-7bab-4321-a4a8-3eb9f936c9bd</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
This sounds like a good question for the datasheet/user manual to
answer.&lt;/p&gt;

&lt;p&gt;
Some processors have one security bit for the flash and a second
security bit for JTAG.&lt;/p&gt;

&lt;p&gt;
But the goal with having a security bit for the flash is to try to
stop all external access to the flash contents, to stop a thief from
making a copy of the program to make cloned units or from retrieving
security keys or similar. It is likely that such a thief has access
to a JTAG adapter so a good chip should have support to either lock
out all JTAG access, or to at least lock out the JTAG interface from
reading the flash. In reality, it isn&amp;#39;t even that simple. A JTAG
interface that is allowed to download program code to RAM, can
download a little application that reads out all flash contents.&lt;/p&gt;

&lt;p&gt;
So your datasheet/user manual should tell you if your chip has a
(at least thought to be) working security implementation or if it is
broken and allows you to circumvent the protection using JTAG.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/thread/103568?ContentTypeID=1</link><pubDate>Wed, 28 Oct 2009 07:58:25 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:f09f5f78-b254-47f4-b115-0cf7ab563341</guid><dc:creator>Tamir Michael</dc:creator><description>&lt;p&gt;&lt;p&gt;
if you set the security bit, you can erase the internal flash
using JTAG but not read it.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/thread/77882?ContentTypeID=1</link><pubDate>Wed, 28 Oct 2009 07:51:46 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:72537de5-f3d8-4b5d-9044-2ef8cd2e2507</guid><dc:creator>Peter Dunno</dc:creator><description>&lt;p&gt;&lt;p&gt;
One more question, can I use JTAG interface after setting the
security bit? If so, I can read on-chip flash using an EFC, can&amp;#39;t
I?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/thread/77877?ContentTypeID=1</link><pubDate>Wed, 28 Oct 2009 06:46:50 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:4c9c45a3-197c-45f6-8618-e665d42c54de</guid><dc:creator>Peter Dunno</dc:creator><description>&lt;p&gt;&lt;p&gt;
Thanks a lot&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: seÑurity bit in AT91SAM7S</title><link>https://community.arm.com/thread/57146?ContentTypeID=1</link><pubDate>Wed, 28 Oct 2009 05:47:21 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:d439d08d-bb62-4225-ba80-4071b0b307ca</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;Hi, i have a question about an access restriction of writing to
on-chip flash after setting the security bit.&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Setting the security bit disables any access to the flash through
external interfaces (ICE/FFP/...). The type of access (read or write)
is not relevant.&lt;/p&gt;

&lt;p&gt;
Internal access to the flash is not affected.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>