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TM4C129 ROM Bootloader

David M. Alter
Guru 61235 points

I have some confusion about the ROM bootloader in TM4C129x devices.  From what I've been able to find, the bootloader invokes automatically if the flash is erased, or can be manually invoked at reset time using a GPIO pin as specified in the BOOTCFG register.

What's confusing me is how the ROM bootloader then decides which mode should be used (e.g., UART, I2C, CAN, SSI, USB, ENET).  I haven't found any documentation describing the decision process of the ROM bootloader.

Thank you,

David

  • 0
    TI__Guru*** 134845 points
    Hi David,

    The ROM boot loader will look at all supported interfaces until one of the interface receives a valid signal, it will then use that interface for the update.

    If multiple interfaces were detected, there is a sequence in which it chooses which is USB > ENET > I2C > SSI > UART.
  • 0 in reply to Ralph Jacobi
    TI__Guru 61235 points
    Ralph,

    Thank you for the reply and the information. It answers my question, but is this documented anyplace?

    Regards,
    David
  • 0 in reply to David M. Alter
    TI__Guru*** 134845 points
    Hello David,

    If it is documented and released publicly, I am not aware. Had to dig through internal resources to find such info. Though I did make note of the lack of documentation on this matter.