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→Boot from eFUSEs
It is worth remebering that, no matter what modes is selected, when processor reset is released, internal Boot ROM is executed. Its behavior depends on selected mode as described in the following sections.
===Boot from eFUSEs===
The term eFUSEs refer refers to an one-time-programmable (OTP) memory integrated in iMX6UL processor. This memory is organized in several 32-bit words. Some of these words - named <code>BOOT_CFG</code> - are used to store configuration bits that affect the boot process, when ''Boot from eFUSEs'' mode is selected. In this case, Boot ROM reads <code>BOOT_CFG</code> words and acts consequently. In particular it tries to retrieve the Program Image [1] from the selected device (NOR flash, NAND flash, SD card etc.), as per <code>BOOT_CFG</code> bits.
BOOT_CFG includes many configuration settings. Some of them are particularly important for the boot strategy:
[1] Program Image includes - but it is not limited to - the code that is executed by the processor when Boot ROM jumps into it.
===Serial downloader===
Serial Downloader mode is used to download a Program Image over one of the following connections:
