Kinetis KV10Z32xx7 self lock problems

[zhitailiu]

Hi, first time design with NXP/Fressscale mcu. In the beginning, I use FRDM KV10Z to develop firmware, it goes pretty well. However, when I first time using my custom PCB with 32 pin LQFP kv10Z32vlc7, sometime the mcu locks himself accidentally! I am using J-Link and KEIL uVsition. Sometime it goes well, but very often my Jlink cannot connect with the mcu and having the following msg:

Once jLink shows these message, I cannot unsecure this mcu anymore, I have to desolder it and replace by a new one. 

I've tried about 10 pcs, now there are 4 of them got locked!

Please help me here. I've spent few days on this, and getting frustrating.

NOTE:

1 Jlink is connected to MCU through SWD_CLK, SWD_IO, Gnd, VCC. Reset_b pin and NMI_b pins are pulled high externally. 

2 I noticed that when the reset_b pin is not pulled high (left open), it goes low by itself. This is quit strange. 

[zhitailiu · Accepted solution]

I just found that J-Flash Lite erase function would case KV10Z32xx7 to secure himself. In this case, the mcus can be unsecure with following steps, found by myself:

1. Power off MCU
2. MCU rst pin (pin19) pull to ground
3. Power on mcu
4. J-link>Unlock Kinetis.
5. Flash a dummy binary or hex file(eg gpio example)

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For those mcus securing themself not because of j-Flash Lite (still unknown for me), the above method is not applicable.

I still have no solution in the case.

[Hui_Ma]

Hi,

There is a document about Kinetis Lock and how to unlock the Kinetis chip.

More detailed info, please check below link:

https://community.nxp.com/docs/DOC-329424 

Have a great day,
Ma Hui

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