Datasheet

AD7731
–12–
REV. 0
Table V. Summary of On-Chip Registers
Power-On/Reset
Register Name Type Size Default Value Function
Communications Write Only 8 Bits Not Applicable All operations to other registers are initiated through
Register the Communications Register. This controls whether
subsequent operations are read or write operations
and also selects the register for that subsequent opera-
tion. Most subsequent operations return control to
the Communications Register except for the continu-
ous read mode of operation.
Status Register Read Only 8 Bits CX Hex Provides status information on conversions, calibra-
tions, settling to step inputs, standby operation and
the validity of the reference voltage.
Data Register Read Only 16 Bits or 24 Bits 000000 Hex Provides the most up-to-date conversion result from
the part. Register length can be programmed to be
16 bit or 24 bit.
Mode Register Read/Write 16 Bits 0174 Hex Controls functions such as mode of operation, uni-
polar/bipolar operation, controlling the function of
AIN3/D1 and AIN4/D0, burnout current and Data
Register word length. It also contains the reference
selection bit, the range selection bits and the channel
selection bits.
Filter Register Read/Write 16 Bits 2002 Hex Controls the amount of averaging in the first stage
filter, selects the fast step and skip modes and con-
trols the chopping modes on the part.
Offset Register Read/Write 24 Bits Contains a 24-bit word which is the offset calibration
coefficient for the part. The contents of this register
are used to provide offset correction on the output
from the digital filter. There are three Offset Regis-
ters on the part and these are associated with input
channel pairs as outlined in Table XIII.
Gain Register Read/Write 24 Bits Contains a 24-bit word which is the gain calibration
coefficient for the part. The contents of this register
are used to provide gain correction on the output
from the digital filter. There are three Gain Registers
on the part and these are associated with input chan-
nel pairs as outlined in Table XIII.
Test Register Read/Write 24 Bits 000000 Hex Controls the test modes of the part which are used
when testing the part. The user is advised not to
change the contents of this register.
NEW
OREZ1WR0WROREZ2SR1SR0SR
YDRYDTS
YBTSFERON3SM2SM1SM0SM
2DM1DM0DM
BU/
NED1D0DLW
FERIH2NR1NR0NROB2HC1HC0HC
11FS01FS9FS8FS7FS6FS5FS4FS
3FS2FS1FS0FSOREZPHCPIKSTSAF
REV. A