BQ27620-G1 Datasheet, PDF (21/45 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

bq27620-G1
www.ti.com
SLUSAE3 – OCTOBER 2012
4.4 ACCESS MODES
The bq27620-G1 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control
data flash access permissions, according to Table 4-6. Data Flash refers to those data flash locations,
specified in Section 4.6, that are accessible to the user.
Security Mode
FULL ACCESS
UNSEALED
SEALED
Table 4-6. Data Flash Access
Data Flash
R/W
R/W
None
Manufacture Info Block
R/W
R/W
R
Although FULL ACCESS and UNSEALED modes appear identical, only FULL ACCESS allows the
bq27620-G1 to write access-mode transition keys.
4.5 SEALING/UNSEALING DATA FLASH
The bq27620-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 bq27620-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 4-2 subcommands.
When in SEALED mode, the CONTROL_STATUS [SS] bit is set, but when the UNSEAL keys are
correctly received by the bq27620-G1, the [SS] bit is cleared. When the full-access keys are correctly
received, then the CONTROL_STATUS [FAS] bit is cleared.
Both the sets of keys for each level are 2 bytes each in length and are stored in data flash. The UNSEAL
key (stored at Unseal Key 0 and Unseal Key 1) and the FULL-ACCESS key (stored at Full-Access Key
0 and Full-Access Key 1) can only be updated when in FULL-ACCESS mode. The order of the keys is
Key 1 followed by Key 0. The order of the bytes entered through the Control( ) command is the reverse of
what is read from the part. For example, if the Key 1 and Key 0 of the Unseal Keys returns 0x1234 and
0x5678, then the Control( ) should supply 0x3412 and 0x7856 to unseal the part.
Copyright © 2012, Texas Instruments Incorporated
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GENERAL DESCRIPTION
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