DS2780 Maxim Integrated Products, DS2780 Datasheet - Page 18

• Manufacturer Part Number: DS2780
• Description: Stand-Alone Fuel Gauge IC
• Manufacturer: Maxim Integrated Products

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Figure 16. EEPROM REGISTER FORMAT
Address
Field
EEC
LOCK
Reserved
BL1
BL0
MEMORY
The DS2780 has a 256 byte linear memory space with registers for instrumentation, status, and control, as well as
EEPROM memory blocks to store parameters and user information. Byte addresses designated as “Reserved”
return undefined data when read. Reserved bytes should not be written. Several byte registers are paired into two-
byte registers in order to store 16-bit values. The most significant byte (MSB) of the 16 bit value is located at a
even address and the least significant byte (LSB) is located at the next address (odd) byte. When the MSB of a
two-byte register is read, the MSB and LSB are latched simultaneously and held for the duration of the read data
command to prevent updates to the LSB during the read. This ensures synchronization between the two register
bytes. For consistent results, always read the MSB and the LSB of a two-byte register during the same read data
command sequence.
EEPROM memory consists of the non-volatile EEPROM cells overlaid with volatile shadow RAM. The Read Data
and Write Data commands allow the 1-Wire interface to directly accesses only the shadow RAM. The Copy Data
and Recall Data function commands transfer data between the shadow RAM and the EEPROM cells. In order to
modify the data stored in the EEPROM cells, data must be written to the shadow RAM and then copied to the
EEPROM. In order to verify the data stored in the EEPROM cells, the EEPROM data must be recalled to the
shadow RAM and then read from the shadow RAM.
USER EEPROM
A 16 byte User EEPROM memory (block 0, addresses 20h - 2Fh) provides non-volatile memory that is
uncommitted to other DS2780 functions. Accessing the User EEPROM block does not affect the operation of the
DS2780. User EEPROM is lockable, and once locked, write access is not allowed. The battery pack or host system
manufacturer can program lot codes, date codes and other manufacturing, warranty, or diagnostic information and
then lock it to safeguard the data. User EEPROM can also store parameters for charging to support different size
batteries in a host device as well as auxiliary model data such as time to full charge estimation parameters.
PARAMETER EEPROM
Model data for the cells, as well as application operating parameters are stored in the Parameter EEPROM
memory (block 1, addresses 60h - 7Fh). The ACR (MSB and LSB) and AS registers are automatically saved to
EEPROM when the RARC result crosses 4% boundaries. This allows the DS2780 to be located outside the
1Fh
2:6
Bit
7
6
1
0
Read Only
Read Only
Read Only
Write to 1
Format
Read /
Bit Definition
Allowable Values
EEPROM Copy Flag
Set to 1 when: Copy Data command executed
Cleared to 0 when: Copy Data command completes
Note: While EEC = 1, writes to EEPROM addresses are ignored
Power-up default: 0
EEPROM Lock Enable
Host write to 1: Enables the Lock command. Host must issue Lock
Cleared to 0 when: Lock command completes or when Lock command
Power-up default: 0
Undefined
EEPROM Block 1 Lock Flag (Parameter EEPROM 60h – 7Fh)
0: EEPROM is not locked
1: EEPROM block is locked
Factory default: 0
EEPROM Block 0 Lock Flag (User EEPROM 20h – 2Fh)
0: EEPROM is not locked
1: EEPROM block is locked
Factory default: 0
command as next command after writing Lock Enable bit to 1.
not the command issued immediately following the Write command
used to set the Lock Enable bit.
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DS2780 Stand-Alone Fuel Gauge IC