AD7709

–15–

REV. PrA

January 2001

PRELIMINARY TECHNICAL DATA

CONFIG14

P3DIG

Digital Input Enable

Set by user to enable P3 as a digital input

Cleared by user to configure as pin P3/AIN3 as analog input. The default configuration is

analog input.

CONFIG13

P2EN

P2 digital output enable bit.

Set by user to enable P2 as a regular digital output pin.

Cleared by user to tristate P2 output.

PSW2 takes presedance over P2EN.

CONFIG12

P1EN

P1 digital output enable bit.

Set by user to enable P1 as a regular digital output pin.

Cleared by user to tristate P1 output.

PSW1 takes presedance over P1EN.

CONFIG11

P4DAT

Digital input port data bit. P4DAT is read only and will return a 0 if P4DIG=0. If P4 is

enabled as a digital input then the read back value indicates the status of pin P4.

CONFIG10

P3DAT

Digital input port data bit. P3DAT is read only and will return a 0 if P3DIG=0. If P3 is

enabled as a digital input then the read back value indicates the status of pin P3.

CONFIG9

P2DAT

Digital output port data bit. P2 is digital output only. When the port is active as an output

(P2EN=1), then the value written to the this data bit appears at the output port. Reading

P2DAT will return what was last written to the P2DAT bit on the AD7709.

CONFIG8

P1DAT

Digital output port data bit. P1 is digital output only. When the port is active as an output

(P1EN=1), then the value written to the this data bit appears at the output port. Reading

P1DAT will return what was last written to the P1DAT bit on the AD7709.

CONFIG7

REFSEL

ADC reference input select.

Cleared by user to select REFIN1(+) and REFIN1(-) as the ADC reference.

Set by user to select REFIN2(+) and REFIN2(-) as the ADC reference.

CONFIG6

CH2

ADC Input Channel Selection bit. Used in conjunction with CH1 and CH0 as shown in

the analog input selection table.

CONFIG5

CH1

ADC Input Channel Selection bit. Used in conjunction with CH2 and CH0 as shown in

the analog input selection table.

CONFIG4

CH0

ADC Input Channel Selection bit. Used in conjunction with CH2 and CH2 as shown in

the analog input selection table.

CH2

CH1

CH0

Positive Input

Negative Input

Buffer

0

0

0

AIN1

AINCOM

Positive Analog Input

0

0

1

AIN2

AINCOM

Positive Analog Input

0

1

0

AIN3

AINCOM

Positive Analog Input

0

1

1

AIN4

AINCOM

Positive Analog Input

1

0

0

AIN1

AIN2

Positive and Negative Analog Inputs

1

0

1

AIN3

AIN4

Positive and Negative Analog Inputs

1

1

0

AINCOM

AINCOM

Positive and Negative Analog Inputs

The final column indicates if the analog inputs are buffered or unbuffered. This determines the common mode

input range on each input. If the input is unbuffered (AINCOM) the common mode input includes GND.

CONFIG3

U N I

Unipolar/Bipolar Operation Selection Bit.

Set by user to enable unipolar operation with straight binary output coding i.e. zero differ-

ential input will result in 0000hex output and a fullscale differential input will result in

FFFF Hex output.

Cleared by user to enable pseudo bipolar operation and offset binary coding, negative

fullscale differential input will result in an output code of 0000 Hex, zero differential in-

put will result in an output code of 8000Hex and a positive fullscale differential input will

result in an output code of FFFF Hex.