BQ27505-J4 Datasheet, PDF (19/38 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

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bq27505-J4
SLVSA40 – DECEMBER 2009
4.3 MANUFACTURER INFORMATION BLOCKS
The bq27505-J4 contains two 32-bytes of user programmable data flash storage: Manufacturer Info
Block A, and Manufacturer Info Block B. 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.
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 bq27505-J4 evaluation software.
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 (A or B, respectively) 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: Manufacturer Info Block A is read-only when in SEALED mode.
4.4 ACCESS MODES
The bq27505-J4 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. Manufacture Information refers to the three 32-byte
blocks.
Security Mode
FULL ACCESS
UNSEALED
SEALED
Table 4-6. Data Flash Access
Data Flash
R/W
R/W
None
Manufacture Information
R/W
R/W
R(A); R/W(B)
Although FULL ACCESS and UNSEALED modes appear identical, only FULL ACCESS allows the
bq27505-J4 to write access-mode transition keys.
4.5 SEALING/UNSEALING DATA FLASH
The bq27505-J4 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 bq27505-J4
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.
When in SEALED mode, the CONTROL_STATUS [SS] bit is set, but when the UNSEAL keys are
correctly received by the bq27505-J4, the [SS] bit is cleared. When the full-access keys are correctly
received, then the CONTROL_STATUS [FAS] bit is cleared.
Copyright © 2009, Texas Instruments Incorporated
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GENERAL DESCRIPTION
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