The BQ34Z100 data flash is a non-volatile memory that contains BQ34Z100 initialization, default, cell status, calibration, configuration, and user information. The data flash can be accessed in several different ways, depending on in what mode the BQ34Z100 is operating and what data is being accessed.

Commonly accessed data flash memory locations, frequently read by a host, are conveniently accessed through specific instructions described in Section 7.2.1. These commands are available when the BQ34Z100 is either in UNSEALED or SEALED modes.

Most data flash locations, however, can only be accessible in UNSEALED mode by use of the BQ34Z100 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 host or changed directly. This is accomplished by sending the set-up command BlockDataControl() (code 0x61) with data 0x00. Up to 32 bytes of data can be read directly from the BlockData() command locations 0x40…0x5F, externally altered, then re-written to the BlockData() command space. Alternatively, specific locations can be read, altered, and re-written 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() (command number 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 in which the desired locations reside. 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 48, 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 + 48 modulo 32 = 0x40 + 16 = 0x40 + 0x10 = 0x50.For example to modify [VOLTSEL] in Pack Configuration from 0 to 1 to enable the external voltage measurement option.

Reading and writing subclass data are block operations 32 bytes in length. Data can be written in shorter block sizes, however. Blocks can be shorter than 32 bytes in length. Writing these blocks back to data flash will not overwrite data that extend beyond the actual block length.