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BQ27500DRZR-V100 Datasheet(PDF) 17 Page - Texas Instruments |
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BQ27500DRZR-V100 Datasheet(HTML) 17 Page - Texas Instruments |
17 / 41 page 4.3 MANUFACTURER INFORMATION BLOCKS 4.4 ACCESS MODES 4.5 SEALING/UNSEALING DATA FLASH bq27500 bq27501 System-Side Impedance Track™ Fuel Gauge www.ti.com SLUS785D – SEPTEMBER 2007 – REVISED APRIL 2008 None of the data written to memory are bounded by the bq27500/1– the values are not rejected by the fuel gauge. Writing an incorrect value may result in hardware failure due to firmware program interpretation of the invalid data. The written data is persistent, so a power-on reset does resolve the fault. The bq27500/1 contains 96 bytes of user programmable data flash storage: Manufacturer Info Block A, Manufacturer Info Block B, Manufacturer Info Block C. 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 bq27500/1 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, 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 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. The bq27500/1 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control data flash access permissions, according to Table 4-6. Public Access refers to those data flash locations, specified in Table 4-7, that are accessible to the user. Private Access refers to reserved data flash locations used by the bq27500/1 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 Section 4.2.1, ACCESSING THE DATA FLASH. Table 4-6. Data Flash Access Security Mode DF – Public Access DF – Private Access FULL ACCESS R/W R/W UNSEALED R/W R/W SEALED R N/A Although FULL ACCESS and UNSEALED modes appear identical, only FULL ACCESS allows the bq27500/1 to write access-mode transition keys. The bq27500/1 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 bq27500/1 via the Control( ) control command. The keys must be sent consecutively, with no other data being written to the Control( ) register between them. Note that to avoid conflict, the keys must be different from the codes presented in the CNTL DATA column of Table 4-2 Control( ) subcommands. Submit Documentation Feedback GENERAL DESCRIPTION 17 |
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