BQ27520-G2 Datasheet, PDF (21/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

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bq27520-G2
SLUSAB7A – MARCH 2011 – REVISED AUGUST 2011
4.3 MANUFACTURER INFORMATION BLOCK
The bq27520-G2 contains 32 bytes of user programmable data flash storage called the Manufacturer
Info Block. The method for accessing these memory locations is slightly different, depending on whether
the device is in UNSEALED or SEALED modes.
When in UNSEALED mode and when and 0x00 has been written to BlockDataControl( ), accessing the
manufacturer information blocks is identical to accessing general data flash locations. First, a
DataFlashClass( ) command is used to set the subclass, then a DataFlashBlock( ) command sets the
offset for the first data flash address within the subclass. The BlockData( ) command codes contain the
referenced data flash data. When writing the data flash, a checksum is expected to be received by
BlockDataChecksum( ). Only when the checksum is received and verified is the data actually written to
data flash.
When in SEALED mode or when 0x01 BlockDataControl( ) does not contain 0x00, data flash is no longer
available in the manner used in UNSEALED mode. Rather than issuing subclass information, a
designated Manufacturer Information Block is selected with the DataFlashBlock( ) command. Issuing a
0x01 or 0x02 with this command causes the corresponding information block to be transferred to the
command space 0x40…0x5f for editing or reading by the system. Upon successful writing of checksum
information to BlockDataChecksum( ), the modified block is returned to data flash. Note: The
Manufacturer Info Block is read-only when in SEALED mode.
4.4 ACCESS MODES
The bq27520-G2 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 Table 4-7, 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
bq27520-G2 to write access-mode transition keys.
4.5 SEALING/UNSEALING DATA FLASH
The bq27520-G2 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 bq27520-G2
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 bq27520-G2, 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 © 2011, Texas Instruments Incorporated
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GENERAL DESCRIPTION
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