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9 Device Configuration
9.1 Commands and Subcommands
The BQ769142 device includes support for direct commands and subcommands. The direct commands are
accessed using a 7-bit command address that is sent from a host through the device serial communications
interface and either triggers an action, provides a data value to be written to the device, or instructs the device to
report data back to the host. Subcommands are additional commands that are accessed indirectly using the 7-bit
command address space and provide the capability for block data transfers. For more information on the
commands and subcommands supported by the device, refer to the
9.2 Configuration Using OTP or Registers
The BQ769142 device includes registers with values that are stored in the RAM and can be loaded automatically
from one-time programmable (OTP) memory. At initial power-up, the device loads OTP settings into registers
that are used by the device firmware during operation. The recommended procedure is for the customer to write
settings into OTP on the manufacturing line in which case the device will use these settings whenever it is
powered up. Alternatively, the host processor can initialize registers after power-up without using the OTP
memory, but the registers need to be reinitialized after each power cycle of the device. Register values are
preserved while the device is in NORMAL, SLEEP, or DEEPSLEEP modes. If the device enters SHUTDOWN
mode, all register memory is cleared, and the device will return to the default parameters (or the OTP
configuration if that has been programmed) when powered again. See the
Manual
for more details.
9.3 Device Security
The BQ769142 device includes three security modes—SEALED, UNSEALED, and FULLACCESS—that can be
used to limit the ability to view or change settings.
•
In SEALED mode, most data and status can be read using commands and subcommands, but only selected
settings can be changed. Data memory settings cannot be changed directly.
•
UNSEALED mode includes SEALED functionality, and also adds the ability to execute additional
subcommands, and read and write data memory.
•
FULLACCESS mode allows capability to read and modify all device settings, including writing OTP memory.
Selected settings in the device can be modified while the device is in operation through supported commands
and subcommands, but in order to modify all settings, the device must enter CONFIG_UPDATE mode (see
Section
13.6), which stops device operation while settings are being updated. After the update is completed, the
operation is restarted using the new settings. CONFIG_UPDATE mode is only available in FULLACCESS mode.
The BQ769142 device implements a key-access scheme to transition among SEALED, UNSEALED, and
FULLACCESS modes. Each transition requires that a unique set of keys be sent to the device through
subcommands. Refer to the
The device provides additional checks which can be used to optimize system robustness, including
subcommands that calculate the digital signature of the integrated instruction ROM and data ROM. These
signatures should never change for a particular product. If these were to change, it would indicate an error:
either that the ROM had been corrupted or the readback of the ROM or calculation of the signature experienced
an error. An additional subcommand calculates a digital signature for the static configuration data (which
excludes calibration values) and compares it to a stored value, returning a flag if the result does not match.
9.4 Scratchpad Memory
The BQ769142 device integrates a 32-byte scratchpad memory for the customer to use to store manufacturing
data, such as serial numbers, production or test dates, and so forth. The scratchpad data can be written into
OTP memory on the customer production line. This data can only be written while in FULLACCESS mode,
although it can be read in all modes.
Copyright © 2021 Texas Instruments Incorporated
BQ769142 Technical Reference Manual
Product Folder Links:
SLUSE91A – SEPTEMBER 2020 – REVISED FEBRUARY 2021
BQ769142 Technical Reference
BQ769142 Technical Reference
for more details.
BQ769142
BQ769142
Manual.
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