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.
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.