Hi,
I work on the kinetis mcu (mk64, mk50) with my own designed pcb and have been using the jlink edu. the board is connected via jtag to jlink. it used to be no problem to program my board that way. however, recently the jlink stopped recognizing the mcu on my board (neither jlink.exe nor gdbserver do). what is also very wield is the following things: when using the pcb with the mk64 as the mcu, jlink.exe can only detect the mcu if I keep the reset pin of the mcu low (the reset pin is connected to a reset button, which i have to keep pressed all the time).
the led on the j-link does not indicate any problems as it is just green and steady without any blinking although the green light flickers. I use the kinetis design studio to program. it works without any problem when I use the evaluation board frdm64 with the onboard sda programmer. I can flash the mcu of the frdm64 board using segger gdbserver without any problem.
hope someone can help!
thanks in advance.

HI Niklas,
thanks for your reply. I use Jlink version 4.98 and 5.0. In both cases the j-link edu was working fine and my board could be programmed without any problem. Just recently it stopped doing so. the only things that has been changed, is that I have upgraded from windows 7 to 10. But I have tried jlink under windows xp - without any success either.
I have attached d the screen shots of the jlink commander window below. I use 2 boards for testing: one board is the mk50dn512cll10 as the mcu, and on the one is the mk64fn1vll12. the image jlink1.jpg shows the result for the mk50 board, image jlink_64 result for the mk64 board, and the last image shows the result for the mk64 board with the reset line kept low (by keeping pressed the reset button (nReset) of my board )

Hi again,
I have tried using the newest version of jlink (5.10). still I cannot connect to the mcu. however, when keeping the nReset low, I couldn't connect to the mcu either. please take a look on the screenshots.
regarding windows, after having installed windows 10, I haven't programmed my board for a while. I only used the frdm64 evaluation board which has been working fine. but there I don't need the jlink edu.

that is already right. the screenshots are taken from the same board. the difference is that the reset line is set low by me for one test while on the other test the reset line is untouched. for the mk50 board I got the same result
see attachment

hi,
my board is individually designed. you are right, with the frdm64 and sda, i don't have any problem either.
anyway, yesterday and this morning the programming all of the sudden worked. I had no problem at all. but now, it suddenly stops again. I don't have any clue why it behaves so randomly.