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Probing the reset_b pin will cause the processor to fail, making it unable to communicate with using jtag link (codewarrior)

Question asked by Olivier Courtois on Aug 4, 2016
Latest reply on Aug 11, 2016 by Fiona Kuang

Hi,

We're using this processor in many of our products.

reset_b pin seems to be really sensitive.

In some cases, probing does not disturbed the processor. But in some other cases, it make him fail, heartbeat is dead and it's not responding reprogramming tool (code warrior) via JTAG interface.

If I probe the reset_b pin (referred to VSS, floating scope) when the processor is finish booting, it does fail.

But if if leave the probe on and put the power on afterwards, it fails.

And when it fail, it fail bad because We're unable to reprogram the processor.

In most cases, when it failed, the reset_b will now toggle on/off (like many many others cases reported by nxp kinetis users).

In other few cases, when it failed, the reset_b will not toggle.

In both behavior, we're stuck anyway; processor does not response to reprogramming tools. Uart's TX is stuck low and there's no heartbeat at all.

 

I can forward you guys some schematic sections.

I've already tried many many many different ways to reprogram the processor (according to nxp community tickets).

 

We got other issues where we try to reprogram using uart interface, and the processor gets bricked just like described above.

We believe that when it got programmed the first time, the tool enabled (by mistake) the secure bit. Afterward, if we reprogram (uart) with mass erase disabled, we kind of get locked inside; unable to reprogram, unable to mass erase.

 

Waiting for your feedback,

Best Regards,

Olivier Courtois

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