ds2786 Maxim Integrated Products, Inc., ds2786 Datasheet - Page 18

• Manufacturer Part Number: ds2786
• Description: Ds2786 Standalone Ocv-based Fuel Gauge
• Manufacturer: Maxim Integrated Products, Inc.

DS2786 Standalone OCV-Based Fuel Gauge
COMMAND REGISTER
The Command Register is read/write accessible. Bit values indicate operations requested to be performed by the
device.
Figure 23. Command Register Format
ADDRESS FEh
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
POR
X
X
X
POCV
SOCV
RCALL
COPY
X—Reserved.
COPY—The Copy bit is set to start a copy command of the scratch pad to EEPROM. A programming voltage must
be present on the VPROG pin prior for the copy to be successful. The COPY bit must be cleared by software within
the t
time window.
PROG
RCALL—The Recall bit is set to recall the contents of EEPROM into the scratch pad.
SOCV—Stored OCV Calculation. This command may be used to reset the Relative Capacity calculation after
updating OCV cell model data in the Scratchpad. When set to one the part is performing an OCV calculation based
on the voltage stored in the Initial Voltage Register, and the OCV lookup table values present in the scratch pad.
Writing the bit to 1 forces a calculation. Forcing an OCV calculation will create capacity estimation error. The bit is
cleared when the hardware completes the calculation.
POCV—Present OCV Calculation. When set to one the part is performing an OCV calculation based on the voltage
stored in the Voltage Register, and the OCV lookup table values present in the scratch pad. Writing the bit to 1
forces a calculation. This function should be used for test purposes only. Forcing an OCV calculation will create
capacity estimation error. The bit is cleared when the hardware completes the calculation.
POR—Power On Reset. A value of 1 starts a power-on reset event. The bit is cleared on the next start or stop on
the 2-Wire bus, exiting the reset state.
USER EEPROM
Location 7Fh provides one byte available for storage of user-defined information. This byte does not affect
operation of the fuel gauge. Factory default is 00h.
2-WIRE BUS SYSTEM
The 2-Wire bus system supports operation as a slave only device in a single or multislave, and single- or
multimaster system. The 2-wire interface consists of a serial data line (SDA) and serial clock line (SCL). SDA and
SCL provide bidirectional communication between the DS2786 slave device and a master device at speeds up to
400kHz. The DS2786’s SDA pin operates bidirectionally, that is, when the DS2786 receives data, SDA operates as
an input, and when the DS2786 returns data, SDA operates as an open-drain output, with the host system
providing a resistive pullup. The DS2786 always operates as a slave device, receiving and transmitting data under
the control of a master device. The master initiates all transactions on the bus and generates the SCL signal as
well as the START and STOP bits which begin and end each transaction.
Bit Transfer
One data bit is transferred during each SCL clock cycle, with the cycle defined by SCL transitioning low-to-high and
then high-to-low. The SDA logic level must remain stable during the high period of the SCL clock pulse. Any
change in SDA when SCL is high is interpreted as a START or STOP control signal.
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