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RF430FRL152H: How do I lock the JTAG on the RF430FRL152H

Part Number: RF430FRL152H


I am trying to understand how to lock the JTAG port on the RF430FRL152H.  The firmware manual describes a JTAG password at address 0xf87d.  If this byte is not 0x39, the ROM code will switch these pins from JTAG function to GPIO.  I have tested this and the byte does have the intended effect.  However, at reset these pins are still being set to JTAG function.  So I can simply use the JTAG programmer to write the correct password and then debug the code in the unlocked state.  How do I configure the processor so that the JTAG pins are configured to GPIO function at reset?

Thank you.

Tom Herron

  • Hello,

    normally the ROM firmware will switch from JTAG functionality to port functionality.
    When you debug the ROM firmware and press in CCS the run button you will loose the JTAG connection.
    To prevent this, you can write 0x39 to address 0xF87D.

    If you want to permanent disable the JTAG port you can write 0x5555 to address 0xFFD0.
    But then there is no way back to get JTAG access again.

    Best regards,
  • Thank you, Helfried.   That is what I needed.  I would be fine with lock being permanent.

    However, I am still not 100% clear on a few points.  After reading your reply, I saw that the JTAG signature is listed in the Datasheet as two words at addresses FFD0 and FFD2.  I then looked at the ap note on MSP JTAG use ( and saw that for FRxx devices, locking the JTAG port requires writing 0x5555 to both signature words.  With that in mind, here are my questions:

    1. Am I correct that this part is categorized as an FRxx part? 
    2. If so, does it require writing both words, or is this part different?
    3. According to the table on page 51 of the ap note, the part is not permanently locked.  Is that because the application itself can still unlock the port by changing the JTAG signature words?

    Thank you for your help.

    Tom Herron

  • Hello Tom,

    1. The part is only similar to the FRxx parts.

    2. Regarding the spec it is an OR. If address 0xFFD0 or 0xFFD2 contains the 0x5555 then the JTAG is locked.

    3. Because the JTAG is locked by data in the memory and not with a "burned" fuse you can think about different ways to change the data again.

    Best regards,


  • Thank you, Helfried.

    That answers my questions.

    Tom Herron