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Booting (bootstrapping) characteristics of i.MX27

Question asked by Federico Strati on May 19, 2016
Latest reply on May 19, 2016 by Federico Strati

There are four (4) BOOT PINS according to the documentation of Freescale on the i.MX27:

<<BOOT [3:0] System Boot Mode Select—The operational system boot mode of the i.MX27/MX27L processor

upon system reset is determined by the settings of these pins. BOOT[1:0] are also used as

handshake signals to PMIC(VSTBY).>>


But, according to some auxiliary docs on evaluation boards, only a single PIN out of the four is actually used:

this single PIN seems to get used in order to differentiate bootstrapping from USB/UART and booting from NAND flash.


I'd like to ask you:

1) if you have any information on the remaining 3 PINs for booting ?

2) if you know how the bootstrap code that runs in internal ROM (iROM) works: as I understand it is used exclusively to bootstrap from UART/USB loading into NAND flash ? Is there a way to know what commands are understood by the iROM code ?

3) I have a legacy product on which a customised version of the "u-boot" bootloader is running: is there a freescale version of "u-boot" for the i.MX27 ?