AD7859/AD7859L

REV. A

–11–

STATUS REGISTER

The arrangement of the status register is shown below. The status register is a read-only register and contains 16 bits of data. The

status register is selected by first writing to the control register and putting two 1s in RDSLT1 and RDSLT0. The function of the

bits in the status register are described below. The power-up status of all bits is 0.

WRITE TO CONTROL REGISTER

SETTING RDSLT0 = RDSLT1 = 1

READ STATUS REGISTER

START

Figure 4. Flowchart for Reading the Status Register

MSB

ZERO

ZERO

SGL/DIFF

CHSLT2

CHSLT1

CHSLT0

PMGT1

PMGT0

ONE

ONE

AMODE

BUSY

CALMD

CALSLT1

CALSLT0

STCAL

LSB

STATUS REGISTER BIT FUNCTION DESCRIPTION

Bit

Mnemonic

Comment

15

ZERO

These two bits are always 0.

14

ZERO

13

SGL/DIFF

Single/Differential Bit.

12

CHSLT2

Channel Selection Bits. These bits, in conjunction with the SGL/DIFF bit, determine which channel has

11

CHSLT1

been selected for conversion. Please refer to Table IIIa and Table IIIb.

10

CHSLT0

9

PMGT1

Power Management Bits. These bits along with the SLEEP pin indicate if the part is in a power-down

8

PMGT0

mode or not. See Table VI in Power-Down Section for description.

7

ONE

Both these bits are always 1.

6

ONE

5

AMODE

Analog Mode Bit. This bit is used along with SGL/DIFF and CHSLT2 – CHSLT0 to determine the

AIN(+) and AIN(–) inputs to the track and hold circuitry and the analog conversion mode (unipolar or bi-

polar). Please see Table III for details.

4

BUSY

Conversion/Calibration BUSY Bit. When this bit is a 1, there is a conversion or a calibration in progress.

When this bit is a zero, there is no conversion or calibration in progress.

3

CALMD

Calibration Mode Bit. A 0 in this bit indicates a self-calibration is selected, and a 1 in this bit indicates a

system calibration is selected (see Table IV).

2

CALSLT1

Calibration Selection Bits. The CALSLT1 and CALSLT0 bits indicate which of the calibration

1

CALSLT0

registers are addressed for reading and writing (see section on the Calibration Registers for more details).

0

STCAL

Start Calibration Bit. The STCAL bit is a 1 if a calibration is in progress and a 0 if there is no calibration in

progress.