I am afraid we have some misunderstanding about "BSL write", "lock/unlock", and "BSL area". On the chip, there is a hardware feature to protect part of the Frame on the chip (with address 0x1000-0x17FF) from being accidentally erased or written. That part of the Flash on the chip is intended to store BSL code (and some other vital constants) and is referred as BSL area. TI always store their version of the factory default BSL code (and some other vital constants) and set the hardware lock during their manufacturing. You normally do not need to erase or write to that area. Thus you normally should not unlock that hardware protection. Now, the factory default BSL code is designed to provide the user a way to eraser write or read all other Flash (as well as RAM and peripheral registers). It is not capable of erasing writing or reading the BSL area itself. Furthermore, when you evoke and run this BSL code, initially, it will only allow you to do a Mass Erase (for all the Flash outside the BSL area) or to enter a password. All other functions of this factory BSL are locked by software, and can only be unlocked by the correct password. The factory BSL code also requires that you use TI's BSL protocol and hardware interface. Thus we have two different part of Flash -- the BSL area and other Flash. We have two different kind of "BSL write" -- write into the BSL area and write into other Flash. And we also have two different kind of "lock/unlock" -- a hardware lock for the BSL area and a software (factory BSL code) lock for other Flash.
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