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TMS320F280039C: DCSM: Can a part be converted to unlocked after CSM OTP is programmed?

BadMonkey
Expert 2090 points
Part Number: TMS320F280039C

The DCSM in the 280039 is quite a bit more complicated, and more capable, than the CSM I have worked with on the 2809, 2812, and 28235 in the past.

The 2809 and 2812 could be returned to an unlocked state by clearing the CSM fields to 0xFFFF. This could be accomplished with CCS by entering the key and then erasing flash. Additionally, it could be accomplished by downloading an "Unlocked" version of the firmware to the unit.

The 28235 could be returned to an unlocked state by powering up with specific pins grounded. Then CCS would only offer the ability to mass erase flash. Once erased, the part is blank and unlocked.

It could be argued that the fact that these can be unlocked means that they are not as secure as they could be (or should be?). However, that depends on the specific product needs.

Looking at the DCSM for the 280039, the keys are stored in OTP. So, there is no opportunity to return the part to an unlocked state by altering the keys. However, I am curious if there is another mechanism to make the part "appear" as unlocked. This is useful for the "Repair Center" and Engineering.

I realize that this would mean the part is not "NSA-level" secured. However, that is not necessary in this case. The older 2809, 2812, & 28235 security was effective enough.

I would like to find a way mimic that older CSM behavior if possible.

  • 0
    TI__Expert 5430 points

    Hi,

    When you say keys, i think you are referring to passwords, because keys are which you provided to unlock a zone once after programming the passwords.

    You are right in saying that keys are stored in OTP which can only be programmed, but not erased. But as far as Unlocking a zone is concerned, you could provide the appropriate keys which match the programmed password locations in the OTP to unlock a zone.

    Having an all FFFF's value for the 128 bit CSMPSWD is not possible anymore that is an incorrect configuration on 280039.

    CSM had a single zone. Technically you can mimic the security settings of a CSM by using DCSM by allocating all the resources to a single zone and control the access to the resources by means of locking/unlocking the zone.

    Hope I have answered your queries. Please revert back if there are any further queries.

    Thanks & Regards
    Pramod