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TM4C129DNCPDT: TDO toggled for initialization fail

Part Number: TM4C129DNCPDT

Hello team, 

Previously I've asked about TDO toggle mechanism, see above history.

My customer returned a unit that I can observe the TDO toggle on them. However our FA report concluded the unit was TNI (trouble not found). So my question is, what kind of self-test the chip performs at initialization and on what condition it outputs TDO toggle? Because from previous discussion when a unit toggles TDO, that means it is unrecoverable. 



  • Hello Jo,

    A toggling TDO tells if the device has locked itself out. Some of the errata where device becomes non-functional use this as a method for lock out detection.

    I don't have further details than to say that the device only toggles TDO output when it cannot be recovered and must be replaced.

  • Greetings,

    As the effort was made to provide (some) feedback - would it not have been (even) more desirable to:

    • toggle that pin at different rates - and/or sequences - to better (i.e. somewhat) convey the failure cause/mechanism?

    Even if not implemented on chip - the respective cause of such, "Loss of Functionality" would, "Aid the user in subsequent PREVENTION!"   That's of FAR greater value - is it not?

    BTW - almost all of our small tech firm's boards contain, "One or more Leds - which identify (thus confirm) proper operation/sequences AND (possible) MCU or external device issues!"

  • Hello cb1,

    Unfortunately, I am not very clear about that portion was designed to work and if there is a differences in the toggling rate then I am not aware of a 'guide' to decode that to something relevant.

  • Greetings Ralph,

    We have, "No such awareness either" - yet such (on chip diagnostics) does appear w/in (certain) other/alien devices - and as such "issues were detected by the MCU" - it (may) have been possible to, "Add far more valuable feedback!"

    When (potentially) destructive implementations are not identified - they are SURE to be REPEATED!    Pity...