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OMAPL137 disabling SPI flash rom after boot up

Bernd Pommerehne
Prodigy 30 points

Hi Forum,

I have a few questions about the OMAPL137 when using a SPI flash on SPI0 for booting and sharing the spi bus. For my application I would like to use a spi flash on spi0 to boot an OMAPL137 processor. For this I would like to use the following boot configuration

BOOT[7]=0,

BOOT[2]=1,

BOOT[1]=0,

BOOT[0]=1,

BOOT[3]=x

It is my understanding from the documentation, that this will shift in the whole program code to ram and run it from there.

1) So after starting the main program, does the OMAPL137 need to access the boot flash any more?

2) Can the flash be powered down (for thermal protection, e.g. by cutting the power using a p channel mos transistor on a gpio pin) safely?

3) I f done so can the SPI0 used with other devices (e.g. an ADC)?

4) What is the recommended way to ensure the proper function of the boot pins at boot time (probably external pull up/down resistors) and later function as SPI interface?

5) Is there an application Note or recommended way to implement this?

6) When powering up the spi flash during run time (E.g. to update the program stored in it) what needs to be considered?

kind regards,

Bernd

  • 0
    Mastermind 6115 points

    Hi Bernd,

    Welcome To E2E Forum.


    1) So after starting the main program, does the OMAPL137 need to access the boot flash any more?


    Yes, we can access spi flash after booting also.
    For example our spi flash size is (10MB), boot image is of 1 MB.
    The Remaining memory i.e 9MB you can use it for whatever purpose.


    4) What is the recommended way to ensure the proper function of the boot pins at boot time (probably external pull up/down resistors) and later function as SPI interface?

    You can refer this wiki to flash SPI flash.

    processors.wiki.ti.com/.../AM1x_DVEVM_Additional_Procedures

  • 0 in reply to Arvind Singh
    Prodigy 30 points

    Hi Arvind,

    Arvind Singh said:
    1) So after starting the main program, does the OMAPL137 need to access the boot flash any more?



    Yes, we can access spi flash after booting also.
    For example our spi flash size is (10MB), boot image is of 1 MB.
    The Remaining memory i.e 9MB you can use it for whatever purpose.

    This question really goes in the direction that I want to disable and disconnect the flash after boot up for thermal protection. My System will see temperatures higher than the rated "maximum temperature under bias" of the flash chip but lower than the rated "maximum storage temperature".

    So when the system sees rising temperatures I want to be able to dynamically turn the flash off and if needed and the temperatures are safe again back on.

    However I can only do this if the OMAPL137 does not need to access it's program for any reason after completing the boot process. So the question is, can I safely remove the device holding the program after boot up?

    Arvind Singh said:

    4) What is the recommended way to ensure the proper function of the boot pins at boot time (probably external pull up/down resistors) and later function as SPI interface?


    You can refer this wiki to flash SPI flash.

    processors.wiki.ti.com/.../AM1x_DVEVM_Additional_Procedures

    thank you for the hint and it might be useful further down the development stream. It seems that this document refers to the OMAPL137 EMV dev board. However I am in the process of designing a new board and look into a way to achieve the initial pin readings without a switch. From the documentation I saw so far pull up/down resistors should be able to produce the initial boot pin reading without limiting the use of the pins for other purposes after booting. However some guidance on a recommended or known to work design would be appreciated.

    best regards,

    Bernd

  • 0 in reply to Bernd Pommerehne
    TI__Mastermind 43660 points

    Hello Bernd,

    This question really goes in the direction that I want to disable and disconnect the flash after boot up for thermal protection. My System will see temperatures higher than the rated "maximum temperature under bias" of the flash chip but lower than the rated "maximum storage temperature".

    Yes, you can disable the power to the flash after boot up. One way to accomplish this by disabling the power to the flash. You need to use separate power controller for flash chip to enable or disable it.

    However I am in the process of designing a new board and look into a way to achieve the initial pin readings without a switch. From the documentation I saw so far pull up/down resistors should be able to produce the initial boot pin reading without limiting the use of the pins for other purposes after booting. However some guidance on a recommended or known to work design would be appreciated.

    It is always recommended to hard wire the boot pins externally. If you do not want to use boot switch, you can simply pull up/down the boot pins externally. The usage of internal resistors would not be reliable.

    Regards,

    Senthil