Datasheet

bq27541-G1
SLUSAL6C –NOVEMBER 2011–REVISED OCTOBER 2012 www.ti.com
SEALING or UNSEALING DATA FLASH
The bq27541-G1 implements a key-access scheme to transition between SEALED, UNSEALED, and FULL-
ACCESS modes. Each transition requires that a unique set of two keys be sent to the bq27541-G1 via the
Control( ) control command. The keys must be sent consecutively, with no other data being written to the
Control( ) register in between. Note that to avoid conflict, the keys must be different from the codes presented in
the CNTL DATA column of Table 2 subcommands.
When in SEALED mode the [SS] bit of CONTROL_STATUS is set, but when the UNSEAL keys are correctly
received by the bq27541-G1, the [SS] bit is cleared. When the full-access keys are correctly received the
CONTROL_STATUS [FAS] bit is cleared.
Both Unseal Key and Full-Access Key have two words and are stored in data flash. The first word is Key 0 and
the second word is Key 1. The order of the keys sent to bq27541-G1 are Key 1 followed by Key 0. The order of
the bytes for each key entered through the Control( ) command is the reverse of what is read from the part. For
an example, if the Unseal Key is 0x56781234, key 1 is 0x1234 and key 0 is 0x5678. Then Control( ) should
supply 0x3412 and 0x7856 to unseal the part. The Unseal Key and the Full-Access Key can only be updated
when in FULL-ACCESS mode.
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