AD7322

Data Sheet

Rev. B | Page 22 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 AD7322 configuration for

the next conversion. Data should be loaded into the control

register after the range register has been initialized. The bit

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

power-up status of all bits is 0).

The two analog input channels can be configured as one pseudo

differential analog input, one true differential input, or two

single-ended analog inputs (see Table 10).

MSB

LSB

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Write

Zero

Register Select

Zero

Zero

ADD0

Mode 1

Mode 0

PM1

PM0

Coding

Ref

Seq1

Seq2

Zero

0

Table 9. Control Register Details

Bit

Mnemonic

Description

12, 11, 1

Zero

These bits should contain 0 during each write to the control register.

10

ADD0

This channel address bit is used to select the analog input channel for the next conversion if the

sequencer is not being used. If the sequencer is being used, this channel address bit is used to select the

final channel in the consecutive sequence (see Table 10).

9, 8

Mode 1,

Mode 0

These bits are used in conjunction with the channel address bit. On the AD7322, the analog inputs can be

configured as single-ended inputs, true differential inputs, or pseudo differential inputs (see Table 10).

7, 6

PM1, PM0

The power management bits are used to select different power mode options on the AD7322 (see Table 11).

5

Coding

This bit is used to select the type of output coding the AD7322 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

Mode 1 = 1, Mode 0 = 0

Mode 1 = 0, Mode 0 =1

Mode 1 = 0, Mode 0 = 0

Channel Address Bit

Mode 1 = 1, Mode 0 = 1

1 Fully Differential Input

1 Pseudo Differential Input

2 Single-Ended Inputs

ADD0

0

Not allowed

AGND

1

Not allowed

AGND