AD7858/AD7858L
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.
START
WRITE TO CONTROL REGISTER
SETTING RDSLT0 = RDSLT1 = 1
READ STATUS REGISTER
Figure 6. Flowchart for Reading the Status Register
MSB
ZERO
BUSY
SGL/DIFF
2/3 MODE
CH2
X
CH1
CH0
PMGT1
PMGT0
STCAL
RDSLT1
RDSLT0
CALMD
CALSLT1
CALSLT0
LSB
STATUS REGISTER BIT FUNCTION DESCRIPTION
Bit
15
Mnemonic
ZERO
Comment
This bit is always 0.
14
BUSY
Conversion/Calibration Busy Bit. When this bit is 1, it indicates that there is a conversion
or calibration in progress. When this bit is 0, there is no conversion or calibration in progress.
13
12
11
10
SGL/DIFF
CH2
CH1
These four bits indicate the channel selected for conversion (see Table III).
CH0
9
8
PMGT1
PMGT0
Power management bits. These bits along with the SLEEP pin will indicate if the part is in a
power-down mode or not. See Table VI for description.
7
6
RDSLT1
RDSLT0
Both of these bits are always 1, indicating it is the status register being read (see Table II).
5
2/3 MODE
Interface Mode Select Bit. With this bit at 0, the device is in Interface Mode 2. With this bit at
1, the device is in Interface Mode 1. This bit is reset to 0 after every read cycle.
4
3
X
Don’t care bit.
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
1
0
CALSLT1
CALSLT0
STCAL
Calibration Selection Bits and Start Calibration Bit. The STCAL bit is read as a 1 if a
calibration is in progress and as a 0 if there is no calibration in progress. The CALSLT1 and
CALSLT0 bits indicate which of the calibration registers are addressed for reading and writing
(see section on the Calibration Registers for more details).
–12–
REV. B
ADI [ ADI ]
