DS2786 Stand-Alone OCV-Based Fuel Gauge

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Write Data Protocol

The write data protocol is used to write to register and shadow RAM data to the DS2786 starting at memory

address Maddr. Data0 represents the data written to Maddr, Data1 represents the data written to Maddr + 1 and

DataN represents the last data byte, written to Maddr + N. The master indicates the end of a write transaction by

sending a STOP or Repeated START after receiving the last acknowledge bit.

S Saddr W A Maddr A Data0 A Data1 A … DataN A P

The MSB of the data to be stored at address Maddr can be written immediately after the Maddr byte is

acknowledged. Because the address is automatically incremented after the least significant bit (LSB) of each byte

is received by the DS2786, the MSB of the data at address Maddr + 1 is can be written immediately after the

acknowledgement of the data at address Maddr. If the bus master continues an auto-incremented write transaction

beyond address 4Fh, the DS2786 ignores the data. Data is also ignored on writes to read-only addresses and

reserved addresses, as well as a write that auto increments to the Function Command Register (address Feh).

Incomplete bytes and bytes that are Not Acknowledged by the DS2786 are not written to memory. As noted in the

Memory Section, writes to EEPROM locations modify the shadow RAM only.

Read Data Protocol

The Read Data protocol is used to read register and shadow RAM data from the DS2786 starting at memory

address specified by Maddr. Data0 represents the data byte in memory location Maddr, Data1 represents the data

from Maddr + 1 and DataN represents the last byte read by the master.

S Saddr W A Maddr A Sr Saddr R A Data0 A Data1 A … DataN N P

Data is returned beginning with the MSB of the data in Maddr. Because the address is automatically incremented

after the LSB of each byte is returned, the MSB of the data at address Maddr + 1 is available to the host

immediately after the acknowledgement of the data at address Maddr. If the bus master continues to read beyond

address FFh, the DS2786 outputs data values of FFh. Addresses labeled “Reserved” in the Memory Map (Table 3)

return undefined data. The bus master terminates the read transaction at any byte boundary by issuing a No

Acknowledge followed by a STOP or repeated START.

PACKAGE INFORMATION

PACKAGE TYPE

PACKAGE CODE

DOCUMENT NO.

10 TDFN-EP

T1033+1

21-0137