Rainbow Electronics DS2788 - Manual (Page 21)

Memory
The DS2788 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 val-
ues. The MSB of the 16-bit value is located at a even
address and the 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 syn-
chronization between the two register bytes. For consis-
tent 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 NV EEPROM cells over-
laid 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. To modify the
data stored in the EEPROM cells, data must be written to
the shadow RAM and then copied to the EEPROM. 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 NV memory that is uncommitted to
other DS2788 functions. Accessing the user EEPROM
block does not affect the operation of the DS2788. User
EEPROM is lockable, and once locked, write access is
not allowed. The battery pack or host system manufac-
turer 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 and application operating
parameters are stored in the parameter EEPROM mem-
ory (block 1, addresses 60h–7Fh). The ACR (MSB and
LSB) and AS registers are automatically saved to EEP-
ROM when the RARC result crosses 4% boundaries.
This allows the DS2788 to be located outside the pro-
tection FETs. In this manner, if a protection device is
triggered, the DS2788 cannot lose more that 4% of
charge or discharge data.
D
S
2
7
8
8
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
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Table 3. Memory Map
ADDRESS (HEX) DESCRIPTION READ/WRITE
00 Reserved R
01 STATUS: Status Register R/W
02 RAAC: Remaining Active Absolute Capacity MSB R
03 RAAC: Remaining Active Absolute Capacity LSB R
04 RSAC: Remaining Standby Absolute Capacity MSB R
05 RSAC: Remaining Standby Absolute Capacity LSB R
06 RARC: Remaining Active Relative Capacity R
07 RSRC: Remaining Standby Relative Capacity R
08 IAVG: Average Current Register MSB R
09 IAVG: Average Current Register LSB R
0A TEMP: Temperature Register MSB R
0B TEMP: Temperature Register LSB R
0C VOLT: Voltage Register MSB R
0D VOLT: Voltage Register LSB R
0E CURRENT: Current Register MSB R
0F CURRENT: Current Register LSB R
10 ACR: Accumulated Current Register MSB R/W*
11 ACR: Accumulated Current Register LSB R/W*