BQ27350 Datasheet, PDF (17/33 Pages) Texas Instruments – Single Cell Li-Ion Battery Manager With Impedance Track Fuel Gauge Technology

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bq27350
Single Cell Li-Ion Battery Manager
With Impedance Track Fuel Gauge Technology
SLUS754 – MARCH 2007
As an example, the data flash location for Manufacturer Info Block B is defined as having a Subclass =
58 and an Offset = 32 through 63 (32 byte block). The specification of Class = "System Data" is not
needed to address Manufacturer Info Block B, but is used instead for grouping purposes when viewing
data flash info in the bq27350 evaluation software.
When in SEALED mode or “0x01” has been written to BlockDataControl( ), 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, 0x02, or 0x03 with this command causes the corresponding information block (A, B, or C,
respectively) to be transferred to the command space 0x40…0x5f for editing or reading by the host. Upon
successful writing of checksum information to BlockDataChecksum( ), the modified block is returned to
data flash. Note: Manufacturer Info Block A is "read only" when in SEALED mode.
4.5 ACCESS MODES
The bq27350 provides three security modes in which control data flash access permissions according to
Table 4-8. Public Access refers to those data flash locations, specified in Table 4-9, that are accessible to
the user. Private Access refers to reserved data flash locations used by the bq27350 system. Care should
be taken to avoid writing to Private data flash locations when performing block writes in Full Access mode,
by following the procedure outlined in ACCESSING THE DATAFLASH.
Table 4-8. Data Flash Access
Security Mode
BOOTROM
FULL ACCESS
UNSEALED
SEALED
DF – Public Access
N/A
R/W
R/W
R
DF – Private Access
N/A
R/W
R/W
N/A
Although FULL ACCESS and UNSEALED modes appear identical, FULL ACCESS allows the bq27350 to
directly transition to BOOTROM mode and write access keys. The UNSEAL mode lacks these abilities.
4.6 SEALING/UNSEALING DATA FLASH ACCESS
The bq27350 implements a key-access scheme to transition between SEALED, UNSEALED, and
FULL-ACCESS modes. Each transition requires that a unique set of 2 keys be sent to the bq27350 via the
Control( ) control command (these keys are unrelated to the keys used for SHA-1/HMAC authentication).
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 selected different from the codes presented in the CNTL DATA
column of Table 4-2 Control( ) subcommands.
When in SEALED mode the Control Status( )’s [SS] bit is set, but when the UNSEAL keys are correctly
received by the bq27350, 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 bytes
entered through the Control( ) command is the reverse of what is read from the part. For example, if the
1st and 2nd word of Unseal Key 0 read returns 0x1234 and 0x5678, then the Control( ) should supply
0x3412 and 0x7856 to unseal the part.
4.7 DATA FLASH SUMMARY
Table 4-9 summarizes the data flash locations available to the user, including their default, minimum, and
maximum values.
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GENERAL DESCRIPTION
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