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TMS320F280049: Can I program the password twice?

Howard Zou
Genius 12365 points
Part Number: TMS320F280049


Hi,

I know the password is located on OTP, but I think we can still modify the password by changing 1 to 0.

For example, at first we program the password to be 1100, then we would like to change it to 1000.

But we face below error when we tried to do so.

  • 0
    TI__Expert 5430 points

    Hi Howard,

    When a password is programmed in the OTP, the respective ECC is also programmed. Just modifying the password by changing from 1 to 0 isn't enough. You need to take care of the corresponding ECC location as well while attempting to modify the password. Hence the error.

    Hope this answers your question.

    Please click on "This resolved my issue" button at the bottom of the post if this response has answered your query.

    Thanks & Regards

    Pramod

  • 0 in reply to Pramod P
    TI__Genius 12365 points

    Pramod,

    excuse me but how can I modify the ECC?

    Isn't ECC automatically calculated and programmed to the corresponding location? Since as you said, the first time we program the password, the respective ECC is also programmed(and it's automatically since we don't do anything for it).

  • +1 in reply to Howard Zou
    TI__Expert 5430 points

    Hi Howard,

    The ECC is calculated and programmed automatically. You are right about that. Let me explain you what I meant with an example.

    Suppose you have programmed the password the first time (from 1111 to 1100 like you mentioned in your example) for which the ECC maybe changed from 1111 to 0101. Now as per your requirement, if you would like to change the password from 1100 to 1000, the ECC for the new data you want to program maybe 1001. As you can see, this is not allowed as there is a transition from 0 to 1 which is not possible and hence the program fails. What I meant in my previous response was "The reason for the error is very likely due to the ECC having bits forced to transition from 0 to 1".

    Hence it is recommended to program the password (and other Zone Select Block contents) only once. If you wish to change the password again, please make use of a different ZSB by moving to the next link pointer.

    Hope this clears your confusion.

    Please click on "This resolved my issue" button at the bottom of the post if this response has answered your query.

    Thanks & Regards

    Pramod