DS2777 MAXIM [Maxim Integrated Products], DS2777 Datasheet - Page 30

• Manufacturer Part Number: DS2777
• Description: 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication
• Manufacturer: MAXIM [Maxim Integrated Products]

2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
The DS2775–DS2778 have 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 des-
ignated as “reserved” typically return FFh when read.
These bytes should not be written. Several byte regis-
ters are paired into 2-byte registers to store 16-bit val-
ues. The MSB of the 16-bit value is located at the even
address and the LSB is located at the next address
(odd) byte. When the MSB of a 2-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 syn-
chronization between the two register bytes. For consis-
tent results, always read the MSB and the LSB of a
2-byte register during the same read data sequence.
EEPROM memory consists of nonvolatile EEPROM cells
overlaying volatile shadow RAM. The read data and
write data protocols allow the 1-Wire interface to direct-
ly accesse the shadow RAM (Figure 21). The Copy
Data and Recall Data Function commands transfer data
between the EEPROM cells and the shadow RAM. In
order to modify the data stored in the EEPROM cells,
data must be written to the shadow RAM and then
copied to the EERPOM. To verify the data stored in the
EEPROM cells, the EEPROM data must be recalled to
Figure 21. EEPROM Access Through Shadow RAM
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INTERFACE
SERIAL
READ
Memory
WRITE
the shadow RAM and then read from the shadow. After
issuing the Copy Data Function command, access to
the EEPROM block is not available until the EEPROM
copy completes (see t
Specification table).
A 16-byte user EEPROM memory (block 0, addresses
20h to 2Fh) provides nonvolatile memory that is uncom-
mitted to other DS2775–DS2778 functions. Accessing
the user EEPROM block does not affect the operation of
the DS2775–DS2778. 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 or warran-
ty or diagnostic information and then lock it to safe-
guard the data. User EEPROM can also store
parameters for charging to support different size batter-
ies in a host device as well as auxiliary model data
such as time to full-charge estimation parameters.
Model data for the cells as well as application operating
parameters are stored in the parameter EEPROM mem-
ory (block 1, addresses 60h to 80h). The ACR (MSB
and LSB) and AS registers are automatically saved to
EEPROM when the RARC result crosses 4% bound-
aries (see Table 8 for more information).
SHADOW RAM
EEPROM
Parameter EEPROM—Block 1
EEC
User EEPROM—Block 0
in the EEPROM Reliability
RECALL
COPY