bootloader sd card

Started by navid, February 21, 2013, 05:38:07 PM

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which boodloader has been used on Imx233 and how it is possible to boot from Sd card ? In the other words in which part of the open source program , information (or code) regarding bootloader ,(bootloader from sd card ) and linux bootloader cab be found ?

Regards ,

Fadil Berisha

Quote from: navid on February 21, 2013, 05:38:07 PM


which boodloader has been used on Imx233 and how it is possible to boot from Sd card ?

After reset, iMX23  begins executing program from internal ROM. The ROM reads boot mode pins to
discover the boot source (USB, SD/MMC, NAND Flash, etc.). Depend of boot source, iMX23  start a
communication with that source and retrieve a boot stream and save it on RAM.

Internal ROM program is not open source software.

A boot stream is a stream of bytes in Safe Boot (SB) format. Boot stream starts with a LOAD command that instructs the ROM to copy the executable into RAM memory. The final JUMP command instructs the ROM to transfer control to the executable that it just loaded. Boot stream is created with tool elftosb supplied by Freescale. Depend of content, there are two types of boot stream's:

1. bootlets + kernel
2. bootloader + kernel

Bootlet is an executable that has been built  for a specific purpose, for example:
- bootlet to configure the internal power supply,
- bootlet to configuresthe clocks and SDRAM.


navid, it's generally as Fadil said - there are right now 2 imx23 bootloaders capable of booting from SD-card:
- linux-prep from Freescale (part of the official Freescale "bootlets")
- U-Boot (but still needs to be enveloped like a Freescale bootlet, so the imx23 ROM can recognize and load it).

Source for the Freescale bootlets is here: