JTAG vs SWD with MCUXpresso and Kinetis K22.

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JTAG vs SWD with MCUXpresso and Kinetis K22.

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LI_Dave
Contributor III

JTAG vs SWD with MCUXpresso and Kinetis K22.  

I have a new PCB with a K22FN512VDC12.  I can connect to the part with a PE Micro Multilink Universal using SWD mode.  All is fine.  

One of the SW developers claims he could Debug in JTAG mode on another K22 board, but if I uncheck the SWD select box in the config for the Multilink with this board it fails to connect to the target.  I am running the latest MCUXpresso version and just loaded the latest driver from PE Micro.   Physical interface is just straight short wires between the CPU and the JTAG conn.  

I am honestly not concerned but before I go too far down this hole I want to understand if this SHOULD work or not.  Is there something special config wise to enable JTAG mode operation?

Dave

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LI_Dave
Contributor III

OK, mystery solved.  I have some bad boards.  TDO was disconnected on the sample PCB that was delivered to me.  Perfectly explains why SWD works and JTAG doesn't!  Appreciate the comments.

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LI_Dave
Contributor III

Hi Erich,

Yes I do have the full JTAG interface connected.   I am really just looking to confirm if this should work. Ideally someone who has connected to a K22 in JTAG mode with a PE Micro Multilink can con confirm this. 

There is the possibility that I have an issue on the PCB with those two extra lines that JTAG requires, but I was wondering if there was anything else you had to do configuration wise to go from SWD to JTAG.

Regards,

Dave

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BlackNight
NXP Employee
NXP Employee

Hi Dave,

Yes, I have used the K22 in JTAG mode. One thing to consider is to have the pins configured for JTAG mode (Processor Expert setting below).

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The other thing is to make sure that the traces are not subject to noise.

I hope this helps,

Erich

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BlackNight
NXP Employee
NXP Employee

Hi David,

For SWD, you need DIO and DCLK, while for JTAG you need 4 pins (TMS, TCK, TDO and TDI).

So for using JTAG, you need these pins available and connected to the debug header.

There is a discussion on this at Using the FRDM-K64F with CodeWarrior | MCU on Eclipse 

I hope that helps,

Erich

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