Data Sheet

AD7323

Rev. B | Page 23 of 36

CONTROL REGISTER

The control register is used to select the analog input channel,

analog input configuration, reference, coding, and power mode.

The control register is a write-only, 12-bit register. Data loaded

on the DIN line corresponds to the AD7323 configuration for

the next conversion. If the sequence register is being used, data

should be loaded into the control register after the range

register and the sequence register have been initialized. The bit

functions of the control register are shown in Table 9 (the power-

up status of all bits is 0).

The four analog input channels can be configured as four single-

ended analog inputs, two true differential input pairs, two

pseudo differential inputs, or three pseudo differential inputs.

MSB

LSB

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Write

Register Select 1

Register Select 2

Zero

ADD1

ADD0

Mode 1

Mode 0

PM1

PM0

Coding

Ref

Seq1

Seq2

Zero

0

Table 9. Control Register Details

Bit

Mnemonic

Description

12, 1

Zero

A 0 should be written to these bits.

11, 10

ADD1, ADD0

These two channel address bits are used to select the analog input channel for the next conversion if the

sequencer is not being used. If the sequencer is being used, the two channel address bits are used to

select the final channel in a consecutive sequence.

9, 8

Mode 1, Mode 0

pins are used in conjunction with the channel address bits. On the AD7323, the analog inputs can be

configured as four single-ended inputs, two true differential input pairs, two pseudo differential inputs, or

three pseudo differential inputs (see Table 10).

7, 6

PM1, PM0

The power management bits are used to select different power mode options on the AD7323 (see Table 11).

5

Coding

This bit is used to select the type of output coding the AD7323 uses for the next conversion result. If

coding = 0, the output coding is twos complement. If coding = 1, the output coding is straight binary.

When operating in sequence mode, the output coding for each channel is the value written to the coding

bit during the last write to the control register.

4

Ref

The reference bit is used to enable or disable the internal reference. If Ref = 0, the external reference is

enabled and used for the next conversion, and the internal reference is disabled. If Ref = 1, the internal

reference is used for the next conversion. When operating in sequence mode, the reference used for each

channel is the value written to the Ref bit during the last write to the control register.

3, 2

Seq1, Seq2

The Sequence 1 and Sequence 2 bits are used to control the operation of the sequencer (see Table 12).

Table 10. Analog Input Configuration Selection

Channel

Address Bits

Mode 1 = 1, Mode 0 = 1

Mode 1 = 1, Mode 0 = 0

Mode 1 = 0, Mode 0 = 1

Mode 1 = 0, Mode 0 = 0

3 Pseudo Differential Inputs

2 Fully Differential Inputs

2 Pseudo Differential Inputs

4 Single-Ended Inputs

ADD1

ADD0

0

0

AGND

0

1

AGND

1

0

AGND

1

1

Not allowed

AGND