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Rest issue in MSP430s

SeaFesse
Expert 2690 points
Other Parts Discussed in Thread: TLV809

Hi TI employee,

    I have a problem  on MSP430 reset that has  surround around  in my head for a long time. This issue occurs quite often if the power ramp quite slow or the VCC drop to a "middle-level" state then power on again, this will lead msp430s to a "dead" satus.

The problem is always easily solved  by adding  a commponet like "tlv809" on MSP430 RST pin .  but it always bring an side effect--------Code download can be a question.

so ...Is there someone can explain  the cause and the solution of this problem clearly for me ?  Thanks in advance.

  • 0
    Guru 46710 points
    CPU operating out of specified VCC/CPU_freq parameter.

    >This issue occurs quite often if the power ramp quite slow or the VCC drop to a "middle-level" state then power on again, this will lead msp430s to a "dead" satus.

    This is happening while CPU is running at default speed (0.8 .. 1MHz) too?
  • 0 in reply to Ilmars
    Expert 2690 points

    Ilmars said:
    This is happening while CPU is running at default speed (0.8 .. 1MHz) too?

    Hi Ilmars,

       I think this situation happes before the CPU  began to run. it's sth more like about the BOR circult issue. and this problem happens  more frequency in F1xx F2xx F4xx than F5xx F6xx or FRxx.  Actually, F5xx F6xx  FRxx. occurs little.

  • 0 in reply to SeaFesse
    Guru 46710 points
    > I think this situation happes before the CPU began to run.
    You shall test instead of think. Most of such problems happen because enginneers *think* they run CPU at allowed frequency while they are not.
  • 0
    Guru 74080 points
    Hi SeaFesse!

    What do you have connected to the Vcc pins and the reset pin of the MSP430? Are there proper caps on the supply lines and do you have the RC filter on RST?

    Dennis
  • 0 in reply to Ilmars
    Expert 2690 points

    Hi Ilmars,

    Yes, CPU runs at allowed frequency absolutely.  And this issue is not a new problem . Many msp430- experienced developers know this issue , however , few 

    can explain it clearly. That's why I ask TI employee for help.

  • 0 in reply to Dennis Eichmann
    Expert 2690 points

    Hello Dennis,
    1uF and 10nF Caps connect to Vcc pin . 10nF/47K (RC) on RST pin.

    In other words, will it be a problem with a 100uF cap connected VCC pin ?

  • 0 in reply to SeaFesse
    Guru 74080 points

    SeaFesse said:
    1uF and 10nF Caps connect to Vcc pin . 10nF/47K (RC) on RST pin.

    OK, so this won't be the problem.

  • 0 in reply to SeaFesse
    Guru 46710 points
    >Yes, CPU runs at allowed frequency absolutely
    If you set CPU frequency at the very beginning of code, without waiting/measuring for VCC to reach nominal level, you can't be absolutely sure that frequency you set - is allowed at given moment. Power voltage could be just 1.5 volts, especially in case "power ramp quite slow".

    >> if the VCC drop to a "middle-level" state then power on again

    For example if you run msp430G2 at frequency that _requires_ 3.3VDC power, like 16MHz, voltage slowly drops to 1.65V and rises up-to 3VDC again then it is expected for CPU to crash due to running out of specs. - BOR won't kick in because it's treshold is around 1.4V.

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