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TM4C123BE6PM: Time for C start-up code

Hideaki Nambu
Mastermind 9165 points
Part Number: TM4C123BE6PM

Hello,
My customer asked the time for the C start-up code to run.
Do you have definition about this?

When they tested the time from "Power-ON" to "main()", the result was 10ms or 17ms.
Therefore they asked this question to understand the variety 10ms or 17ms.

I would like to ask them to signal the reset release by a GPIO or communication, but we are glad if you could satisfy customer's point.

  • 0
    TI__Guru*** 135355 points
    Hello Nambu-san,

    I don't believe we have any specs for how long it makes to reach main(). Even if we did, they would have to come with an asterisk anyways.

    The reason being is that when the device boots up, there is some ROM code that executes first.

    Part of the execution in ROM includes checking for if the device should enter ROM Boot Loader.

    Depending on the state of the MCU and what could possibly execute from ROM, as well as the state of the RST pin, this varied window could make a lot of sense.

    Note that Digital POR will trigger the internal Reset that takes typically 9 ms but up to 11.5 ms, which would explain the bulk of the delay.

    How are they determining the timing of when main() executes?

    Are they seeing a difference with the exact same device and the exact same software loaded? Or is the variance observed due to differences with the device setup/software?

    Also, is the difference exactly either 10 ms or 17 ms, or is it varied and just falls between 10-17 ms?