iMX6 JTAG_MOD as GPIO

[dmitrykolyadint]

Hello,

We are using IMX6UL (MCIMX6G3CVM05AB) for custom board and due to limited number of pins want to use JTAG_MOD as GPIO output. At the same time we want to use JTAG for system debug during development phase.

RM 45.2 states that "this pin is sampled at TRST reset to determine mode of operation" - does that mean that changing this pin to GPIO output high after startup (when TRST is high) won't affect JTAG operation? JTAG_TRST is not used and is pulled high permanently.

Thanks,

Dmitry

[sidebranch]

Artur, why cannot JTAG_MOD be used as GPIO?

And if it cannot, why is this not mentioned in the manual?

Thanks, Leon.

[dmitrykolyadint]

Thank you Artur.

[art · Accepted solution]

Although i.MX6UL RM shows the SW_MOD_CTRL register for the JTAG_MOD pad, there is no way to use this pad for any alternate function other than JTAG_MOD, otherwise, the processor may lock. So, there is no way to use the JTAG_MOD pad as GPIO.

Have a great day,
Artur

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[jakepollex]

Artur,

Does the same apply to the IMXRT1060?  I was thinking of using this pin as a GPIO and didn't know if this problem also exists on the RT1060.  I tested it out and I am able to toggle the GPIO and still debug using SWD.  Please let me know your thoughts.

Thanks,

Jake