AD7993 Analog Devices, AD7993 Datasheet - Page 24

• Manufacturer Part Number: AD7993
• Description: 4-Channel, 10-Bit ADC with I2C Compatible Interface in 16-Lead TSSOP
• Manufacturer: Analog Devices

Specifications of AD7993

• Resolution (bits): 10bit
• # Chan: 4
• Sample Rate: 188kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: SOP

AD7993/AD7994
WRITING TO THE AD7993/AD7994
Depending on the register being written to, there are three
different writes for the AD7993/AD7994.
WRITING TO THE ADDRESS POINTER REGISTER
FOR A SUBSEQUENT READ
In order to read from a particular register, the address pointer
register must first contain the address of that register. If it does
not, the correct address must be written to the address pointer
register by performing a single-byte write operation, as shown
in Figure 26. The write operation consists of the serial bus
address followed by the address pointer byte. No data is
written to any of the data registers. A read operation may be
subsequently performed to read the register of interest.
WRITING A SINGLE BYTE OF DATA TO THE ALERT
STATUS REGISTER OR CYCLE REGISTER
The alert status register, configuration register and the cycle
register are 8-bit registers, so only one byte of data can be
written to each. Writing a single byte of data to one of these
registers consists of the serial bus write address, the chosen
data register address written to the address pointer register,
followed by the data byte written to the selected data register.
See Figure 27.
SDA
SCL
SDA
SCL
START BY
MASTER
START BY
MASTER
0
1
0
1
1
1
SERIAL BUS ADDRESS BYTE
Figure 26. Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation
SERIAL BUS ADDRESS BYTE
0
0
FRAME 1
A3
A3
FRAME 1
SCL (CONTINUED)
SDA (CONTINUED)
A2
A2
A1
A1
A0
A0
Figure 27. Single-Byte Write Sequence
R/W
R/W
AD7993/AD7994
AD7993/AD7994
ACK. BY
Rev. 0 | Page 24 of 32
ACK. BY
9
9
9
C4
C4
D7
1
1
1
C3
C3
D6
WRITING TWO BYTES OF DATA TO A LIMIT OR
HYSTERESIS REGISTER
Each of the four limit registers are 16-bit registers, so two bytes
of data are required to write a value to any one of them. Writing
two bytes of data to one of these registers consists of the serial
bus write address, the chosen limit register address written to
the address pointer register, followed by two data bytes written
to the selected data register. See Figure 28.
If the master is write addressing the AD7993/AD7994, it can
write to more than one register. After the first write operation
has completed for the first data register in the next byte, the
master writes to the address pointer byte to select the next data
register for a write operation. This eliminates the need to
readdress the device in order to write to another data register.
ADDRESS POINTER REGISTER BYTE
ADDRESS POINTER REGISTER BYTE
C2
C2
D5
C1
C1
D4
FRAME 2
DATA BYTE
FRAME 2
FRAME 3
P3
P3
D3
P2
P2
D2
P1
D1
P1
P0
AD7993/AD7994
P0
D0
AD7993/AD7994
AD7993/AD7994
ACK. BY
ACK. BY
ACK. BY
9
9
9
STOP BY
MASTER
STOP BY
MASTER