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ULINK: Unlocking a Freescale Kinetis L device with Reset pin disabled

Information in this knowledgebase article applies to:

  • MDK4.60 and lower


When the reset pin of a Freescale Kinetis KL0, KL1 or KL2 device was disabled in the nonvolatile option byte FOPT (see bit RESET_PIN_CFG in startup code startup_MKLxxxx.s), ULINK cannot connect to this device after that. Even a mass erase was not possible with the reset pin disabled.


ULINK needed the RESET pin of a microcontroller to bring it into a defined status.


The attached version of ULINK drivers (ULINK2/ULINK-ME/ULINKpro) fixes this issue by automatically using the MDM-AP debug registers instead of the reset pin if necessary. These driver files are only compatible for MDK-ARM version 4.60. Later releases will already include this improvement. Please download this ZIP file and extract it to the \Keil\ARM\BIN folder of your MDK installation.

Please note that disabling the reset pin and disabling the SWD/JTAG debug pins will lock-out debugging and flash programming completely.


  • Refer to Debug in the ULINK2 User's Guide.



Request the files attached to this knowledgebase article.

Last Reviewed: Tuesday, April 4, 2017

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