AD7923

Data Sheet

Rev. D | Page 12 of 24

CONTROL REGISTER DESCRIPTIONS

The control register on the AD7923 is a 12-bit, write-only

register. Data is loaded from the DIN pin of the AD7923 on the

falling edge of SCLK. The data is transferred on the DIN line at

the same time that the conversion result is read from the part.

The data transferred on the DIN line corresponds to the

AD7923 configuration for the next conversion. This requires

16 serial clocks for every data transfer. Only the information

provided on the first 12 falling clock edges (after CS falling

edge) is loaded to the control register. MSB denotes the first bit

in the data stream. The bit functions are outlined in Table 5.

Table 5. Control Register Bit Functions

MSB

LSB

WRITE

SEQ1

DONTC

DONTC

ADD1

ADD0

PM1

PM0

SEQ0

DONTC

RANGE

CODING

Table 6.

Bit

Name

Description

11

WRITE

The value written to this bit of the control register determines whether the following 11 bits are loaded to the

control register. If this bit is a 1, the following 11 bits are written to the control register. If it is a 0, the remaining

11 bits are not loaded to the control register and it remains unchanged.

10

SEQ1

The SEQ1 bit in the control register is used with the SEQ0 bit to control the use of the sequencer function (see

Table 9).

7–6

ADD1

ADD0

These two address bits are loaded at the end of the present conversion and select which analog input channel is

converted in the next serial transfer, or they can also be used to select the final channel in a consecutive sequence,

as described in Table 9. The selected input channel is decoded, as shown in Table 7. The next channel to be

converted on is selected by the mux on the 14th SCLK falling edge. Channel address bits corresponding to the

conversion result are also output on the DOUT serial data stream prior to the 12 bits of data (see the Serial Interface

section).

5, 4

PM1

PM0

Power management bits. These two bits decode the mode of operation of the AD7923, as shown in Table 8.

3

SEQ0

The SEQ0 bit in the control register is used with the SEQ1 bit to control the use of the sequencer function.

(see Table 9).

2, 9–8

DONTC

Don’t care.

1

RANGE

This bit selects the analog input range to be used on the AD7923. If it is set to 0, the analog input range extends from

0

CODING

This bit selects the type of output coding the AD7923 uses for the conversion result. If this bit is set to 0, the output

coding for the part is twos complement. If this bit is set to 1, the output coding from the part is straight binary (for

the next conversion).

Table 7. Channel Selection

ADD1

ADD0

Analog Input Channel

0

0

0

1

1

0

1

1