SLUUCP8 June 2024 BQ41Z50
UNSEALED to FULL ACCESS instructs the device to allow full access to all SBS commands and data flash. The BQ41Z50 device is shipped from TI in this mode. The keys for UNSEALED to FULL ACCESS can be read and changed via the SecurityKey() MAC command when in FULL ACCESS mode. Changing from UNSEALED to FULL ACCESS is performed by using the ManufacturerAccess() command, by writing the first word of the Full Access Key to ManufacturerAccess(), followed by the second word of the Full Access Key to ManufacturerAccess(). The two words must be sent within 4 s. In FULL ACCESS mode, the command to go to boot ROM can be sent.
If the gauge is sealed, it will always return to the SEALED state after POR even if the gauge is unsealed prior to a POR. If the SREC of a sealed gauge is extracted and then programmed into another gauge, the other gauge will also power up in the SEALED state. The only way to permanently restore the UNSEALED state is to reflash the gauge with an unsealed SREC.