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TM4C129DNCPDT: TDO toggles when device fails initialization

Part Number: TM4C129DNCPDT

Hi Tiva experts,

The datasheet mentioned that "if the device fails to initialization during reset, the hardware toggles the TDO output as an indication of failure."

My question is what kind of failure is that TDO able to toggle a pulse? My customer wondered if it can be used to identify some failure cases, such as flash damaged, no oscillation, pin pads damage, etc.

Thanks,

Jo

  • Hello Jo,

    If the TDO toggle occurs with a fixed frequency then that indicates that something has gone wrong during the process of boot up of the device, and if that occurs it is a sign that the device cannot be recovered and must be replaced.

    So in that regard, yes it can be used to identify a failure case, but it happens rarely and would mean that the device is unrecoverable.

    In most cases we use the TDO toggle in the opposite manner, which is to confirm if the device has NOT been irreparably damaged and that an Unlock process may yet recover it.

  • Greetings Ralph,

    Left this one for 'youse guys' - as my (motley) crüe (hardly) qualify as Tiva experts.   (TiVO - another story...)

    Jo Chen said:
    My customer wondered if it can be used to identify some failure cases, such as flash damaged, no oscillation, pin pads damage, etc.

    My group believes that the customer is, 'On to something here - although 'burdening TDO' w/such a task - seems unwise!'   

    Perhaps consider:

    • would not the measure of other & added elements - add to this customer's intent?   (i.e. measuring Supply Voltage, other 'critical signals or levels')
    • pin/pads may be measured - for 'serious designs' that's (often) a requirement.   Usually achieved via a 'SO-PI Shift Register(s)' (serial out, parallel in) which places minimal signal demands upon the MCU - yet enables a substantial number of MCU pins/pads to be monitored - quickly & easily!
    • note that 'pins beyond TDO alone are (already) required - thus 'one added GPIO' - outputting unique signal sequences (flashes) to an on-board Led - provides a far superior means of, 'Identifying such Failure Cases!'    And w/no possibility - of disrupting the TDO signal...

    Fleshed out - as detailed (& restricted) above - seems to achieve the 'best of both worlds.'   (i.e. 'Safe TDO & Diagnostic Capability - w/out conflict/compromise!)