Rainbow Electronics DS2756 - Manual (Page 16)

DS2756: High-Accuracy Battery Fuel Gauge with Programmable Suspend Mode
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MEMORY
The DS2756 has a 256-byte linear address space with registers for instrumentation, status, and control in the lower
32 bytes, with lockable EEPROM and SRAM memory occupying portions of the remaining address space. All
EEPROM and SRAM memory is general-purpose except addresses 31h, 33h, 34h and 35h, which should be
written with the default values for the Status Register, Accumulation Bias Register, Charge Suspend Threshold and
Discharge Suspend Threshold, respectively. If the Suspend interrupt is not used, addresses 34h and 35h can be
used as general purpose EEPROM. When the MSB of any two-byte register is read, the MSB and LSB values are
latched and held for the duration of the Read Data command. This prevents updates during the read to ensure
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. In describing register control and status bits, the
terms set and clear refer to internal operations which manipulate bit values. The terms read and write refer to 1-
Wire access to the bit values. Several bits are set internally but require the host system to write them to a 0 value.
EEPROM memory is shadowed by RAM to eliminate programming delays between writes and to allow the data to
be verified by the host system before being copied to EEPROM. The Read Data and Write Data protocols to/from
EEPROM memory addresses access the shadow RAM. The Recall Data function command transfers data from the
EEPROM to the shadow RAM. The Copy Data function command transfers data from the shadow RAM to the
EEPROM and requires t
EEC
to complete programming of the EEPROM cells. In unlocked EEPROM blocks, writing
data updates shadow RAM. In locked EEPROM blocks, the Write Data command is ignored. The Copy Data
function command copies the contents of shadow RAM to EEPROM in an unlocked block of EEPROM but has no
effect on locked blocks. The Recall Data function command copies the contents of a block of EEPROM to shadow
RAM regardless of whether the block is locked or not.
Figure 14. EEPROM Access via Shadow RAM
Serial
Interface
Write
Read
Shadow RAM
EEPROM
Copy
Recall