BQ27520-G3 Datasheet, PDF (19/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

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bq27520-G3
SLUSAP0 – DECEMBER 2011
4.1.2.5 BlockDataChecksum( ): 0x60
UNSEALED Access: This byte contains the checksum on the 32 bytes of block data read or written to
data flash. 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 the
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.
4.1.2.6 BlockDataControl( ): 0x61
UNSEALED Access: This command is used to control data flash access mode. Writing 0x00 to this
command enables BlockData( ) to access general data flash. Writing a 0x01 to this command enables
SEALED mode operation of DataFlashBlock( ).
SEALED Access: This command is not available in SEALED mode.
4.1.2.7 ApplicationStatus( ): 0x6a
This byte function allows the system to read the bq27520-G3 Application Status data flash location. See
Table 6-1 for specific bit definitions.
4.1.2.8 Reserved — 0x6b–0x7f
4.2 DATA FLASH INTERFACE
4.2.1 ACCESSING THE DATA FLASH
The bq27520-G3 data flash is a non-volatile memory that contains bq27520-G3 initialization, default, cell
status, calibration, configuration, and user information. The data flash can be accessed in several different
ways, depending on what mode the bq27520-G3 is operating in and what data is being accessed.
Commonly accessed data flash memory locations, frequently read by a system, are conveniently
accessed through specific instructions, already described in Section 4.1, DATA COMMANDS . These
commands are available when the bq27520-G3 is either in UNSEALED or SEALED modes.
Most data flash locations, however, are only accessible in UNSEALED mode by use of the bq27520-G3
evaluation software or by data flash 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 flash locations individually, the block containing the desired data flash 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 data flash, once the correct checksum for the whole block
is written to BlockDataChecksum( ) (0x60).
Occasionally, a data flash CLASS will be larger than the 32-byte block size. In this case, the
DataFlashBlock( ) command is used to designate which 32-byte block the desired locations reside in. The
correct command address is then given by 0x40 + offset modulo 32. For example, to access Terminate
Voltage in the Gas Gauging class, DataFlashClass( ) is issued 80 (0x50) to set the class. Because the
offset is 45, it must reside in the second 32-byte block. Hence, DataFlashBlock( ) is issued 0x01 to set the
block offset, and the offset used to index into the BlockData( ) memory area is 0x40 + 45 modulo 32 =
0x40 + 13 = 0x40 + 0x0d = 0x4d.
Copyright © 2011, Texas Instruments Incorporated
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GENERAL DESCRIPTION
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