AD7731 Analog Devices, AD7731 Datasheet - Page 20

• Manufacturer Part Number: AD7731
• Description: Low Noise, High Throughput 24-Bit Sigma-Delta ADC
• Manufacturer: Analog Devices

Specifications of AD7731

• Resolution (bits): 24bit
• # Chan: 3
• Sample Rate: 5MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni
• Ain Range: (2Vref/PGA Gain) p-p,(Vref/PGA Gain) p-p
• Adc Architecture: Sigma-Delta
• Pkg Type: DIP,SOIC,SOP

AD7731
READING FROM AND WRITING TO THE ON-CHIP REGISTERS
The AD7731 contains a total of twelve on-chip registers. These registers are all accessed over a three-wire interface. As a result,
addressing of registers is via a write operation to the topmost register on the part, the Communications Register. Figure 5 shows a
flowchart for reading from the different registers on the part summarizing the sequence and the words to be written to access each of
the registers. Figure 6 gives a flowchart for writing to the different registers on the part, again summarizing the sequence and words
to be written to the AD7731.
Register
Status Register
Data Register
Mode Register
Filter Register
Offset Register
Gain Register
*N/A = Not Applicable. Continuous reads of these registers does
Register
Communications Register
Data Register
Mode Register
Filter Register
Offset Register
Gain Register
Test Register
not make sense as the register contents would remain the same
since they are only changed by a write operation.
Byte W
(Hex)
10
11
12
13
15
16
Byte Y (Hex)
00
Read Only Register.
02
03
05
06
User is advised not
to change contents of
Test Register
Byte Y
20
21
(Hex)
22
N/A*
N/A*
N/A*
Figure 5. Flowchart for Reading from the AD7731 Registers
Figure 6. Flowchart for Writing to the AD7731 Registers
Byte Z
(Hex)
30
30
30
N/A*
N/A*
N/A*
–20–
COMMUNICATIONS REGISTER
(SEE ACCOMPANYING TABLE)
WRITE BYTE W TO
READ REGISTER
CONTINUOUS
REQUIRED?
READS OF
REGISTER
START
NO
COMMUNICATIONS REGISTER
(SEE ACCOMPANYING TABLE)
YES
WRITE TO REGISTER
WRITE BYTE Y TO
START
NO
COMMUNICATIONS REGISTER
(SEE ACCOMPANYING TABLE)
(SEE ACCOMPANYING TABLE)
COMMUNICATIONS REGISTER
END
WRITE BYTE Y TO
WRITE BYTE Z TO
READ REGISTER
CONTINUOUS
OPERATION?
READ
STOP
YES
REV. 0
REV. A