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PGA305EVM-034: EEPROM_LOCK

Koji Hayashi92
Mastermind 7030 points

Part Number: PGA305EVM-034

Hi TI-team

My customer wrote 1 to the EEPROM_LOCK bit, so the EEPROM must be locked.

But they were able to write to EEPROM.

Isn't it correct that IC is not writable ?

What is the role of this BIT ?

They want to make sure that the EEPROM cannot be modified when they ship the product.

Please let me know if there is a way to lock the EEPROM.

　

Best  Regards,

Koji Hayashi

  • 0
    TI__Guru**** 181021 points

    Hi Koji,

    Our normal PGA guru is on holiday this week, so let me share my interpretation of the PGA305 datasheet with you.  Table 20, 4th line, shows the EEPROM_LOCK register as a RW register, which implies the EEPROM can be locked and unlocked.  It does not appear to be a 'fused lock' that would keep the user out of the EEPROM at some point in the future.

  • 0 in reply to Tom Hendrick
    Mastermind 7030 points

    Hi Tom-san

    Thank you for response.

    If the customer sets this bit to 1, wouldn't the EEPROM not be able to be written ?

    If it is correct that they cannot write in, they may be following the wrong procedure.

    Could you please tell me the procedure that will prevent me from writing ?

     

    Best Regards,

    Koji Hayashi

  • 0 in reply to Koji Hayashi92
    TI__Guru**** 181021 points

    Hi Koji,

    Yes, that is my interpretation - writing a 1 to D0 of the EEPROM_LOCK register prevents writing to the EEPROM.

  • 0 in reply to Tom Hendrick
    Mastermind 7030 points

    Hi Tom-san

    I checked with my customer.

    They used the GUI to write the EEPROM.

    After writing with "EEPROM_LOCK" locked as shown below, they changed the value of another part (e.g. the value of PGAIN) and tried to write it.

    As a result, the changed part was changed.

    If we use the GUI to write, isn't it written after the Lock is released ? 

    Please confirm the writing procedure of the GUI.

    Customers are still only able to write in the GUI and cannot get confirmation of writing in other ways.

     

    Best Regards,

    Koji Hayashi

  • 0 in reply to Koji Hayashi92
    TI__Guru**** 181021 points

    Hi Koji,

    Scott will confirm the GUI lock operation.

  • 0 in reply to Tom Hendrick
    TI__Mastermind 31655 points

    Hi Koji-san,

    The EEPROM lock is enabled when you set the lock bit, however the GUI itself supplies an unlock code when the PGA305 is put into digital interface mode. This allows the EEPROM to be read or written through the GUI. 

    You should be able to test that the EEPROM lock is successful by manually resetting the PGA305 using the low-level configuration page of the GUI and setting the COMPENSATION_CONTROL register to 0x03. This will allow digital interface communication, but will not send the EEPROM unlock code, and you can confirm that it is not possible to read or write to the EEPROM.

    Regards,

  • 0 in reply to Scott Cummins
    Mastermind 7030 points

    Hi Scott-san

    Thank you for response.

    I will answer my customer

     

    Best Regards,

    Koji Hayashi