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<section begin="Body" /> =Introduction=Boot process and bootstrap configuration==
NXP iMX6UL processor implements a very flexible boot process. This versatility comes at the price of a non trivial bootstrap configuration scheme. Typical system-on-module (SOM for short) adopter does not need to deal with such a complexity. In other words, he/she expects to manage few boot configuration issues because it is assumed that most of them are "hidden" within the SOM itself. Nevertheless, there are specific applications where the system integrator needs full control of all the bootstrap configuration options, even if the design is built upon a SOM.
It is worth remembering that an exhaustive discussion of this issue is beyond the scope of this article. For more details, please refer to <ref name="IMX6ULRM">NXP, IMX6ULRM, ''i.MX 6UltraLite Applications Processor Reference Manual''</ref>.
==Overview of NXP =iMX6UL bootstrap processoverview===
When it comes to boot process, three factors play a major role:
*BOOT_MODE signals (<code>BOOT_MODE1</code>, <code>BOOT_MODE0</code>)
[3] It means it is set to 1.
==Options for =AXEL ULite usersboot options===
From the point of view of boot configuration programming, AXEL ULite portfolio consists of two basic categories of ordering codes:
#part numbers in the form DLTx0xx'''0'''0x2R have eFUSEs not programmed
For convenience, the products belonging to the first category will be denoted as ''NP-eFUSE''. The others will be referred as ''P-eFUSE''.
====P-eFUSE ordering codes====
P-EFUSE codes address users that don't need full control of boot configuration and can use one of the preconfigured options. These configurations are intended to satisfy most commonly used boot schemes. Nevertheless, '''users are strongly recommended to understand the limitations of such configurations in order to verify they meet system requirements'''.
This leads to three different boot flows and that are shown in the following pictures.
=====NAND-NOR option=====
This configuration makes use of NAND flash as primary internal boot device. NOR flash is used as secondary boot device where, for example, a so-called ''golden image'' of the bootlader can be stored.
=====NAND-only option=====
This configuration makes use of NAND flash as primary - and only - internal boot device. [[File:AXELULite-boot-NAND.png|thumb|center|750px|Boot flow for ordering code in the form DLTx0xx'''2'''0x2R]]
=====NOR-NAND option=====
This configuration makes use of NOR flash as primary internal boot device. Nevertheless, NAND flash is available for generic storage. NAND flash can not be used as booting device.
P-eFUSE products yet provides a moderated freedom in terms of configurability and openness. Generally speaking, this may affect system security. '''Hence it is strongly recommended that system integrator does a detailed assessment in case he/she is considering the use of P-eFUSE SOMs, especially if security concerns are relevant'''.
====NP-eFUSE ordering codes====
Users who need to have the '''full control''' of the boot process should choose one of the NP-eFUSE part numbers. This allows them to be able to
*program eFUSEs by themselves
*decide to use ''GPIO override'' approach even for mass production.
=====AXEL ULite adapter=====
To ease the development effort of the customers working with NP-eFUSE SOMs, DAVE Embedded Systems has made available a specific adapter board. For more information please see [[AXEL ULite adapter|this page]].
===References==={{=reflist}}
