DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface

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Read Data Protocol

The Read Data protocol is used to read register and shadow RAM data from the DS2764 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 most significant bit (msb) of the data in MAddr. Because the address is

automatically incremented after the least significant bit (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 DS2764 outputs data values of FFh. Addresses labeled

“Reserved” in the memory map 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.

Function Command Protocol

The Function Command protocol executes a device specific operation by writing one of the function command

values (FCmd) to memory address FEh. Table 4 lists the DS2764 FCmd values and describes the actions taken

by each. A one byte write protocol is used to transmit the function command, with the MAddr set to FEh and the

data byte set to the desired FCmd value. Additional data bytes are ignored. Data read from memory address FEh

is undefined.

S SAddr W A MAddr=0FEh A FCmd A P

Table 4. Function Commands

FUNCTION

COMMAND

TARGET

EEPROM

BLOCK

FCMD

VALUE

DESCRIPTION

0

42h

1

44h

Copy Data

2

48h

This command copies the shadow RAM to the target EEPROM block.

Copy Data commands that target locked blocks are ignored. While the

Copy Data command is executing, the EEC bit in the EEPROM register is

set to 1, and Write Data commands with MAddr set to any address within

the target block are ignored. Read Data and Write Data commands with

MAddr set outside the target block are processed while the copy is in

and starts after the FCMD byte is acknowledged. Subsequent Copy or

Lock commands must be delayed until the EEPROM programming cycle

completes.

0

B2h

1

B4h

Recall Data

2

B8h

This command recalls the contents of the targeted EEPROM block to its

shadow RAM.

0

63h

1

66h

Lock

2

6Ah

This command locks (write-protects) the targeted EEPROM block. The

LOCK bit in the EEPROM register must be set to 1 before the lock

command is executed. If the LOCK bit is 0, the lock command has no

effect. The lock command is permanent; a locked block can never be

and starts after the FCMD byte is acknowledged. Subsequent Copy or

Lock commands must be delayed until the EEPROM programming cycle

completes.

Note: EEPROM block 2 is not supported on special order devices with unique IDs.