Cannot program MK64FN1M0M12. Reset problem.

[rothkarl]

Hello everyone!

I have just produced a board which uses a MK64FN1M0VLQ12 chip.

The problem is that the chip's reset pin stays low after POR, and I cannot figure out how could I achive to pull its pin high.

The power supply of the chip seems to be ok, the reset pin is tighted through 1K resisitor towards positive rail, and through 100 nF cap to ground.

I am trying to probram my chip using FRDM-K64F board, but as soon I plug its SWD socket, the programmer's reset LED turns on, signing that the common reset line is low. So at this point I have no chance to program the chip.

I think I can rule out systematic hardware failure, the reset pin is not shorted toward ground, the power supplying shall be fine.

My question is, what can lead for this chip to hold its reset pin low?

Thank you in advance!

[rothkarl]

It seems like the problem became solved. I have decided to put two 33 ohm resistors in series with data and clock line, and Voila now it works :smileyhappy:

[PabloBaena]

Hi Roth, 

Following post was useful for me, regarding reset ping waveform for a new/blank chip.

https://community.nxp.com/message/602948?commentID=602948#comment-602948 

Also, have you check NMI pin state? It must be high in a new chip, even if left floating.

You also could check stability of SWD_CLK signal on the scope. I've found it's quite vulnerable to interference.  In my board, I had to vary cable length of SWD port in order for a successful programming. It seems like some kind of strange waveform appears and its reduced by longer cable configuration, (which of course implies that my own board is not high resistent to interferences and needs a revision.)

By the way, in my setup , reset pin is not pulled up., just floating.

Hope this helps!

Paul

[rothkarl]

Your suggestion led me to find the solution for the problem.

The problem is that the FRDM-K64F demo board doesnt have serial terminating resistors on data and clock lines, which make almost impossible to probram an external chip with a longer cable,

Lesson learned.

Thank you for your help, I really appreciate it!

[PabloBaena]

Hello Roth, glad to know it worked for you!.  I will setup the 33 ohm resistors in my board too.

Regards,

Paul

[rothkarl]

So additional info:

Chip is supplied from 3.3 V LDO. I have tried decreasing power up slew rate with a serial 33 Ohm and parallel 20 uF cap. But it doesn't help at all.

The Vregin and vout33 pins tighted through 10 k resistor to ground.

In a previous design this power scheme was used, and it worked.

I am looking forward for some help from NXP support team as well!

Thank you in advance!