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nPORRST vs nRST

Eugene K
Expert 1685 points

What is difference in internal behavior between nPORRST vs nRST pins of TMS570. In some cases I can not bring  device out "lockup" if I only use nRST. I have observed this at least  after JTAG re-flash and after terminating CCS debug session.

Eugene

  • 0
    TI__Genius 14205 points

    Hi Eugene,

    Could you please give more details about the "lockup"  

    See the below comments from our expert.

    " Asserting nPORRST resets all debug logic as well, while asserting nRST does not. This would be the most likely explanation for their debug tool look-up. You can ask him to assert nTRST as well along with the nRST. This will reset all debug logic along with the main core logic."

    Regards
    Prathap

  • 0 in reply to Prathap
    Expert 1685 points

    Hi Prathap,

    First of all, it is not our debug tool its is CCS.

    'Lockup' might not be the right word and this is why I originally put it into "". In the context of my question "lockup" means that after I reflash device with Flash470 I can not start my SW with just nRST signal. I have to use nPORRST to bring device out of some type of not running mode. All of this has nothing to do with debugger or even Flash470. It is device behavior.

    The main concern however, if nRST signal can reliably bring device to a known state in the case of error. For instance, if I connect nERROR to nRST will it guarantee that device aways (I mean always) be reset and ready to execute from 0x0? I am afraid that we will not be able to use nTRST in our product.

    Thanks,

    Eugene

  • 0 in reply to Eugene K
    TI__Genius 14205 points

    Hi Eugene

    What Emulator are you using to Flash the device?

    Pls see the below comments from the concerned Engineer.

    The operations: “flashing the part”, or “terminating CCS” also indicate that the JTAG state machine was used to halt the CPU and then make it execute commands scanned in via the JTAG state machine. If they cannot assert nTRST manually, isn’t there an option in sdopts.cfg to assert nTRST each time the JTAG is disconnected? I am not sure sdopts.cfg is still used or not, but that would be, or would have been, the best option to assert nTRST.

    If that is not an option, then asserting nPORRST is the only choice left. nRST does not reset the JTAG state machine, which could still be holding the CPU in halt mode so that it cannot execute any code.