nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

RE: nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

Simonr — Wed, 09 Jul 2025 09:24:48 GMT

Glad to hear that you got it working, and thank you for sharing your solution with the rest of the community.

RE: nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

szamos — Tue, 08 Jul 2025 18:58:48 GMT

Hi Simon,

I figured that Win 8.1 not being supported may be in the official reply, and I was proven right. ;-)

In any case, last night I uninstalled and then reinstalled EWB, and it is working fine now. As for what may have caused it -- I installed Segger J-Flash *after* EWB (for DevAcademy), and because it detected that EWB is using an older version of the J-Link driver it updated it. I haven't verified it so I can't be 100% certain, but I think that there is a better than 50% chance that it was the J-Flash install and update that broke EWB.

RE: nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

Simonr — Mon, 07 Jul 2025 13:46:58 GMT

I see you're working on Windows 8.1. Support for that Windows OS version ended on January 10th, 2023 so we can't expect this to run on your side. I'd strongly suggest upgrading to Windows 10 or 11 and then consider moving to the nRF Connect SDK.

Best regards,

Simon

RE: nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

szamos — Fri, 04 Jul 2025 19:56:18 GMT

After some poking around in EWB I found where I can set JTAG speed: Project -> Options... -> J-Link/J0-Trace.

I tried many different manual values between 100 kHz and 1250 kHz to no avail. The only thing changed that I no longer get the "Auto speed detection..." message, which is fully expected.

Questions:

1. What exactly is RAMCode, and where is it located? I would tend to think that some corrupted SW/FW is much more likely than a HW issue, but since I have this board for less than a week, I obviously do not know enough about the board.

2.Is it possible to verify the state of the flash from the nRF_USB connector? If yes, how?

3. Is it possible to use and program the board through the nRF_USB connector? If yes, how?

RE: nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

szamos — Fri, 04 Jul 2025 17:50:37 GMT

I've tried installing the NCS SDK using the DevAcademy instructions and it failed. That was before the flash erase issue with EWB. Will post that later.

I did search for issue I'm having and at least one poster had the exact same issue, but using a different toolchain, though underneath, EWB may be using the same J-Flash driver. In the case of the other poster It was a hardware issue because a different board worked, but I do not have another board to try, and I do know for the fact that it worked initially.

The previous issue: devzone.nordicsemi.com/.../j-flash-failed-to-erase-chip

RE: nRF 52840-DK fails execution with undefined instruction (CFSR.UNDEFINSTR)

Turbo J — Fri, 04 Jul 2025 09:50:06 GMT

Ditch the old SDK software, start over in VS code with the NCS SDK.