MK20DN128VFM5 - SWD Does not connect

[mjg8t]

Hi There,

I am now having problmes getting a custom desing to connect with the MK20DN128VFM5.  I finally figured out an unconnecting SWD issue on a previous custom K22F board  that I thought I might be having the same issue on - not the case.  Previously the problem was the NMI triggering interrupts which would not allow SWD connection (k22f - no longer connects to SWD ) - reference: k22f - no longer connects to SWD .

Based upon the reference manual section 6.3.4 the only pins that would conflict with the SWD connection process are the NMI/EZ_PORT_CS(PTA4)  and the reset pins.  However, I have ensured the that PTA4 is held high during the boot process, observed the reset pin coming high after power on and SWD will not connect.

• I have previously designed a board with a PK20 (pre-qualified 1n86b silicon) chip pcb which have used in the past and based this current design on the working design. 
• I test the MK20 1n86B silicon chip on the previously running custom board and it will not connect to SWD. 
• I test the PK20 1n86B on my new board and it connects to SWD no problem
• I test the MK20 Nn86B on the K22F freedom board (SDA chip location) and it will not connect using SWD.
• I pull an Mk20 3n86B (latest silicon version) chip off of a K22F freedom board and test it on my current design and it connects no problems!

Questions:

1. So it appears that the issue is within the MK20 1n86B silicon version of the chip and I cannot find any reason that SWD would not connect based upon all of the information in the silicon errata.  Any further ideas to what might be causing this silicon version to not properly boot/ connect to SWD?
2. The easy solution would be to get a hold of the latest silicon version MK20 3n86B chips.  I just ordered some MK20DN128VFM5 from digikey and I recieved the old 1n86B silicon chips.  Is there anyway to order and ensure I receive the latest silicon?

[Hui_Ma]

Hi M J,

I have a FRDM-K20D50M board on hand, which with a K20 50MHz mask set: 1N86B on board.

I can use J-Link with SWD to debug this board.

So, I think the mask set 1N86B is not the root cause.

I would recommend customer to refer FRDM-K20D50M schematics about SWD interface design.

And which debugger tool customer is using? Segger J-Link or P&E Multilink Universal?

Thank you for the attention.

IAR debugger setting:

Have a great day,
Ma Hui

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[mjg8t · Accepted solution]

Hi Ma,

Thank you for confirming that you have a 1n86B version running on your fdm-k22F board.  I have re-soldered a 1n86B chip onto the freedom board and it is connecting to SWD on my side as well.  I have found that our custom footprint could be improved for better soldering repeatability.  I have gotten the 1n86B chips working on our custom prototype boards as well after reworking the boards a few times for proper soldering connections.

It appears I led us on a bit of a goose chase based upon some bad soldering from the beginning.  I will see if I can re-label the topic to better reflect the problem. 

Thanks for the support!