AD7329

Rev. 0 | Page 26 of 40

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 AD7329 configuration for the next

conversion. If the sequence register is being used, data should be loaded into the control register after the range registers and the sequence

register have been initialized. The bit functions of the control register are shown in Table 11 (the power-up status of all bits is 0).

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

ADD2

ADD1

ADD0

Mode 1

Mode 0

PM1

PM0

Coding

Ref

Seq1

Seq2

Weak/

Three-State

0

Table 11. Control Register Details

Bit

Mnemonic

Description

12, 11, 10

ADD2, ADD1,

ADD0

These three 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 three 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 AD7329, the analog inputs can be

configured as eight single-ended inputs, four fully differential input pairs, four pseudo differential inputs,

or seven pseudo differential inputs (see Table 12).

7, 6

PM1, PM0

The power management bits are used to select different power mode options on the AD7329 (see Table 13).

5

Coding

This bit is used to select the type of output coding the AD7329 uses for the next conversion result. If the

coding = 0, the output coding is twos complement. If the 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 ref-

erence 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 14).

1

Weak/Three-State

This bit selects the state of the DOUT line at the end of the current serial transfer. If the bit is set to 1, the

DOUT line is weakly driven to Channel Address Bit ADD2 of the following conversion. If this bit is set to 0,

DOUT returns to three-state at the end of the serial transfer (see the Serial Interface section).

The eight analog input channels can be configured as seven pseudo differential analog inputs, four pseudo differential inputs, four true

differential input pairs, or eight single-ended analog inputs.

Table 12. Analog Input Configuration Selection

Mode 1 = 1, Mode 0 = 1

Mode 1 = 1, Mode 0 = 0

Mode 1 = 0, Mode 0 =1

Mode 1 = 0, Mode 0 = 0

Channel Address Bits

7 Pseudo Differential I/Ps

4 Fully Differential I/Ps

4 Pseudo Differential I/Ps

8 Single-Ended I/Ps

ADD2

ADD1

ADD0

0

0

0

AGND

0

0

1

AGND

0

1

0

AGND

0

1

1

AGND

1

0

0

AGND

1

0

1

AGND

1

1

0

AGND

1

1

1

Temperature indicator

AGND