Data Sheet

AD7739

Rev. A | Page 13 of 32

REGISTER DESCRIPTIONS

Table 11. Register Summary

Addr

Dir

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Register

(hex)

Default Value

Communications

0x00

W

0

R/W

6-bit register address

I/O Port

0x01

R/W

P0

P1

P0 DIR

P1 DIR

RDYFN

REDPWR

0

Sync

P0 pin

P1 pin

1

1

0

0

0

0

Revision

0x02

R

Chip revision code

Chip generic code

x

x

x

x

1

0

0

1

Test

0x03

R/W

24-bit manufacturing test register

ADC Status

0x04

R

RDY7

RDY6

RDY5

RDY4

RDY3

RDY2

RDY1

RDY0

0

0

0

0

0

0

0

0

Checksum

0x05

R/W

16-bit checksum register

ADC Zero-Scale Calibration

0x06

R/W

24-bit ADC zero-scale calibration register

0x80 0000

ADC Full-Scale Calibration

0x07

R/W

24-bit ADC full-scale register

0x80 0000

Channel Data1

0x08 to

0x0F

R

16-/24-bit data registers

0x8000

Channel Zero-Scale

Calibration1

0x10 to

0x17

R/W

24-bit channel zero-scale calibration registers

0x80 0000

Channel Full-Scale

Calibration1

0x18 to

0x1F

R/W

24-bit channel full-scale calibration registers

0x20 0000

Channel Status1

0x20 to

0x27

R

CH2

CH1

CH0

0/P0

RDY/P1

NOREF

Sign

OVR

Channel number

0

0

0

0

0

Channel Setup1

0x28 to

0x2F

R/W

BUFOFF

COM1

COM0

Stat OPT

Enable

RNG2

RNG1

RNG0

0

0

0

0

0

0

0

0

Channel Conversion Time1

0x30 to

0x37

R/W

Chop

FW (7-bit filter word)

1

0x11

Mode2

0x38 to

0x3F

R/W

MD2

MD1

MD0

CLKDIS

Dump

Cont RD

24/16 bit

Clamp

0

0

0

0

0

0

0

0

1

The three LSBs of the register address, that is, Bit 2, Bit 1, and Bit 0 in the communications register, specify the channel number of the register being accessed.

2

The AD7739 has only one mode register, although the mode register can be accessed in one of eight address locations. The address used to write the mode register

specifies the ADC channel on which the mode is applied. Only Address 0x38 must be used for reading from the mode register.

Table 12. Operational Mode Summary

MD2

MD1

MD0

Mode

0

0

0

Idle

0

0

1

Continuous conversion

0

1

0

Single conversion

0

1

1

Power-down (standby)

1

0

0

ADC zero-scale self-calibration

1

0

1

ADC full-scale self-calibration (for 2.5 V)

1

1

0

Channel zero-scale system calibration

1

1

1

Channel full-scale system calibration

Table 13. Input Range Summary

RNG2

RNG1

RNG0

Nominal Input Voltage Range

1

0

0

±2.5 V

1

0

1

+2.5 V

0

0

0

±1.25 V

0

0

1

+1.25 V

0

1

0

±0.625 V

0

1

1

+0.625 V