REV. F

AD7712

–9–

Control Register (24 Bits)

A write to the device with the A0 input low writes data to the control register. A read to the device with the A0 input low accesses the

contents of the control register. The control register is 24 bits wide and when writing to the register 24 bits of data must be written

otherwise the data will not be loaded to the control register. In other words, it is not possible to write just the first 12 bits of data into

the control register. If more than 24 clock pulses are provided before

TFS returns high, then all clock pulses after the 24th clock

pulse are ignored. Similarly, a read operation from the control register should access 24 bits of data.

MSB

MD2

MD1

MD0

G2

G1

G0

CH

PD

WL

X

BO

B/U

FS11

FS10

FS9

FS8

FS7

FS6

FS5

FS4

FS3

FS2

FS1

FS0

X = Don’t Care.

LSB

Operating Mode

MD2

MD1

MD0

Operating Mode

000

Normal Mode. This is the normal mode of operation of the device whereby a read to the device accesses

data from the data register. This is the default condition of these bits after the internal power-on reset.

001

Activate Self-Calibration. This activates self-calibration on the channel selected by CH. This is a one-step

calibration sequence, and when complete, the part returns to normal mode (with MD2, MD1, MD0 of

the control registers returning to 0, 0, 0). The

DRDY output indicates when this self-calibration is complete.

For this calibration type, the zero-scale calibration is done internally on shorted (zeroed) inputs, and the

010

Activate System Calibration. This activates system calibration on the channel selected by CH. This is a

two-step calibration sequence, with the zero-scale calibration done first on the selected input channel and

DRDY indicating when this zero-scale calibration is complete. The part returns to normal mode at the

end of this first step in the two-step sequence.

011

Activate System Calibration. This is the second step of the system calibration sequence with full-scale

calibration being performed on the selected input channel. Once again,

DRDY indicates when the full-

scale calibration is complete. When this calibration is complete, the part returns to normal mode.

100

Activate System Offset Calibration. This activates system offset calibration on the channel selected by

CH. This is a one-step calibration sequence and, when complete, the part returns to normal mode with

DRDY indicating when this system offset calibration is complete. For this calibration type, the zero-scale

101

Activate Background Calibration. This activates background calibration on the channel selected by CH. If

the background calibration mode is on, then the AD7712 provides continuous self-calibration of the

reference and shorted (zeroed) inputs. This calibration takes place as part of the conversion sequence,

extending the conversion time and reducing the word rate by a factor of 6. Its major advantage is that

the user does not have to worry about recalibrating the device when there is a change in the ambient

continuously monitored, and the calibration registers of the device are automatically updated.

110

Read/Write Zero-Scale Calibration Coefficients. A read to the device with A0 high accesses the contents

of the zero-scale calibration coefficients of the channel selected by CH. A write to the device with A0 high

writes data to the zero-scale calibration coefficients of the channel selected by CH. The word length for

reading and writing these coefficients is 24 bits, regardless of the status of the WL bit of the control

register. Therefore, when writing to the calibration register, 24 bits of data must be written; otherwise the

new data will not be transferred to the calibration register.

111

Read/Write Full-Scale Calibration Coefficients. A read to the device with A0 high accesses the contents of

the full-scale calibration coefficients of the channel selected by CH. A write to the device with A0 high

writes data to the full-scale calibration coefficients of the channel selected by CH. The word length for

reading and writing these coefficients is 24 bits, regardless of the status of the WL bit of the control

register. Therefore, when writing to the calibration register, 24 bits of data must be written; otherwise the

new data will not be transferred to the calibration register.