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Previous: <a href="Atmel-STK600.html#Atmel-STK600" accesskey="p" rel="prev">Atmel STK600</a>, Up: <a href="Programmer-Specific-Information.html#Programmer-Specific-Information" accesskey="u" rel="up">Programmer Specific Information</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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<h3 class="section">5.2 Atmel DFU bootloader using FLIP version 1</h3>
<p>Bootloaders using the FLIP protocol version 1 experience some very
specific behaviour.
</p>
<p>These bootloaders have no option to access memory areas other than
Flash and EEPROM.
</p>
<p>When the bootloader is started, it enters a <em>security mode</em> where
the only acceptable access is to query the device configuration
parameters (which are used for the signature on AVR devices). The
only way to leave this mode is a <em>chip erase</em>. As a chip erase
is normally implied by the <samp>-U</samp> option when reprogramming the
flash, this peculiarity might not be very obvious immediately.
</p>
<p>Sometimes, a bootloader with security mode already disabled seems to
no longer respond with sensible configuration data, but only 0xFF for
all queries. As these queries are used to obtain the equivalent of a
signature, AVRDUDE can only continue in that situation by forcing the
signature check to be overridden with the <samp>-F</samp> option.
</p>
<p>A <em>chip erase</em> might leave the EEPROM unerased, at least on some
versions of the bootloader.
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