BQ27425-G1 Datasheet, PDF (16/32 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated Sense Resistor

bq27425-G1
SLUSAI6 – NOVEMBER 2011
www.ti.com
BlockDataChecksum( ): 0x60
UNSEALED Access: This byte contains the checksum on the 32 bytes of block data read or written. The
least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] , for x the
least-significant byte) before being written to 0x60.
SEALED Access: This byte contains the checksum for the 32 bytes of block data written to Manufacturer Info
Block. The least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] , for x
the least-significant byte) before being written to 0x60.
BlockDataControl( ): 0x61
UNSEALED Access: This command is used to control the data access mode. Writing 0x00 to this command
enables BlockData( ) to access general data NVM. Writing a 0x01 to this command enables SEALED mode
operation of DataBlock( ).
SEALED Access: This command is not available in SEALED mode.
DeviceNameLength( ): 0x62
UNSEALED and SEALED Access: This byte contains the length of the Device Name.
DeviceName( ): 0x63…0x69
UNSEALED and SEALED Access: This block contains the device name that is programmed in Device Name
Reserved – 0x6a – 0x7f
BLOCK DATA INTERFACE
Accessing Block Data
The bq27425 contains both re-writable EEPROM non-volatile memory (NVM) and ROM-based data blocks. Upon
device RESET, the ROM-based data blocks are copied to associated volatile RAM space to initialize default
configuration and data constants to be used by the fuel gauging algorithm. Re-writable NVM-based data blocks
contain information expected to change such as: calibration, customer data and Impedance Track fuel gauging
data tables. If the application requires a change to the NVM or RAM configuration data, the host can update the
data blocks in CONFIG UPDATE mode. RAM-based data changes are temporary and must be applied by the
host using CONFIG UPDATE mode after each device RESET; while changes to the NVM data blocks are
permanent. The data blocks can be accessed in several different ways, depending on the access mode and what
data is being accessed.
Commonly accessed data block locations, frequently read by a system, are conveniently accessed through
specific instructions, already described in Section Data Commands. These commands are available when the
bq27425 is either in UNSEALED or SEALED modes.
Most data block locations, however, are only accessible in UNSEALED mode by use of the bq27425 evaluation
software or by data block transfers. These locations should be optimized and/or fixed during the development
and manufacture processes. They become part of a golden image file and can then be written to multiple battery
packs. Once established, the values generally remain unchanged during end-equipment operation.
To access data locations individually, the block containing the desired data NVM location(s) must be transferred
to the command register locations, where they can be read to the system or changed directly. This is
accomplished by sending the set-up command BlockDataControl( ) (0x61) with data 0x00. Up to 32 bytes of data
can be read directly from the BlockData( ) (0x40…0x5f), externally altered, then rewritten to the BlockData( )
command space. Alternatively, specific locations can be read, altered, and rewritten if their corresponding offsets
are used to index into the BlockData( ) command space. Finally, the data residing in the command space is
transferred to the associated data block, once the correct checksum for the whole block is written to
BlockDataChecksum( ) (0x60).
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