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Re: Cortex-Mx MCUs with SWD access locked

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On 6/24/2022 19:26, David Brown wrote:
> On 24/06/2022 16:42, dalai lamah wrote:
>> Un bel giorno pozz digitò:
>>
>>>> Or maybe some ground loops, for example if you have connected the 
>>>> J-Link
>>>> probe to a desktop PC (or in general a PC not isolated from mains) 
>>>> and your
>>>> boards are somewhat connected to mains or earth ground too.
>>>
>>> Yes, I use a desktop PC connected to mains and the boards are supplied
>>> from an AC/DC connected to mains too.
>>>
>>> Is this a problematic scenario?
>>
>> Normally it shouldn't be, but it also depends on what the board does. 
>> If it
>> contains some power stages running at high frequency, it is quite common
>> (especially if the EMI filtering is subpar) that switching currents can
>> pass through the AC/DC power supply and create problems.
>>
>> If this keeps happening, try using a laptop isolated from mains and 
>> see if
>> it helps.
>>
> 
> Another trick is to make sure you have a separate ground connection 
> between the board and the PC before attaching the JTAG.  A wire from the 
> board ground to the PC's case is usually fine.
> 

That might definitely help. I have seen sparks between a DUT and
the scope probe GND more than once.
But most importantly one has to learn to quickly identify when a part
has been blown.
[which is easy to say
of course, I remember some 10-12 years ago how I spent at least 3 days
to figure out why a 5200B was not completing the boot process, after
some disk activity etc.. Turned out I had killed it (tampering with the
1.5V core power regulator, most likely) in a way *one* of its cachelines
had one of its longwords damaged.... I did all the investigation - just
think tracing through the boot process (no debug port, just the CPU)
because I was not very experienced in replacing a BGA.... well, had to
acquire the experience it took, it was stressful but I managed :) ].

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Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-23 23:38 +0200
  Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-24 11:25 +0200
    Re: Cortex-Mx MCUs with SWD access locked dalai lamah <antonio12358@hotmail.com> - 2022-06-24 12:22 +0200
      Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-24 16:27 +0200
        Re: Cortex-Mx MCUs with SWD access locked dalai lamah <antonio12358@hotmail.com> - 2022-06-24 16:42 +0200
          Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-24 16:56 +0200
            Re: Cortex-Mx MCUs with SWD access locked dalai lamah <antonio12358@hotmail.com> - 2022-06-24 17:16 +0200
          Re: Cortex-Mx MCUs with SWD access locked David Brown <david.brown@hesbynett.no> - 2022-06-24 18:26 +0200
            Re: Cortex-Mx MCUs with SWD access locked Dimiter_Popoff <dp@tgi-sci.com> - 2022-06-24 20:00 +0300
            Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-27 08:54 +0200
              Re: Cortex-Mx MCUs with SWD access locked David Brown <david.brown@hesbynett.no> - 2022-06-27 09:23 +0200
    Re: Cortex-Mx MCUs with SWD access locked David Brown <david.brown@hesbynett.no> - 2022-06-24 14:15 +0200
      Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-24 16:25 +0200
        Re: Cortex-Mx MCUs with SWD access locked Stef <me@this.is.invalid> - 2022-06-24 20:29 +0200
          Re: Cortex-Mx MCUs with SWD access locked David Brown <david.brown@hesbynett.no> - 2022-06-24 20:34 +0200
            Re: Cortex-Mx MCUs with SWD access locked Stef <me@this.is.invalid> - 2022-06-24 22:12 +0200
              Re: Cortex-Mx MCUs with SWD access locked David Brown <david.brown@hesbynett.no> - 2022-06-25 10:19 +0200
          Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-27 09:06 +0200
            Re: Cortex-Mx MCUs with SWD access locked David Brown <david.brown@hesbynett.no> - 2022-06-27 09:25 +0200
        Re: Cortex-Mx MCUs with SWD access locked Reinhardt Behm <rbehm@hushmail.com> - 2022-06-26 14:25 +0000
          Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-27 10:07 +0200
            Re: Cortex-Mx MCUs with SWD access locked Reinhardt Behm <rbehm@hushmail.com> - 2022-06-27 15:11 +0000
              Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-27 23:50 +0200
                Re: Cortex-Mx MCUs with SWD access locked Stef <me@this.is.invalid> - 2022-06-28 11:23 +0200
                Re: Cortex-Mx MCUs with SWD access locked pozz <pozzugno@gmail.com> - 2022-06-28 12:42 +0200
                Re: Cortex-Mx MCUs with SWD access locked Stef <me@this.is.invalid> - 2022-06-28 17:06 +0200

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