AD7997 Analog Devices, AD7997 Datasheet - Page 23

• Manufacturer Part Number: AD7997
• Description: 8-Channel, 10-Bit ADC with I2C Compatible Interface in 20-Lead TSSOP
• Manufacturer: Analog Devices

Specifications of AD7997

• Resolution (bits): 10bit
• # Chan: 8
• Sample Rate: 79kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: SOP

SERIAL INTERFACE
Control of the AD7997/AD7998 is carried out via the I
compatible serial bus. The devices are connected to this bus as
slave devices under the control of a master device, such as the
processor.
SERIAL BUS ADDRESS
Like all I
7-bit serial address. The 3 MSBs of this address for the AD7997/
AD7998 are set to 010. The AD7997/AD7998 come in two
versions, the AD7997-0/AD7997-0 and AD7997-1AD7998-1.
The two versions have three different I
which are selected by either tying the address select pin, AS, to
AGND or V
different addresses for the two versions, up to five AD7997/
AD7998 devices can be connected to a single serial bus, or the
addresses can be set to avoid conflicts with other devices on the
bus. (See Table 6.)
The serial bus protocol operates as follows.
The master initiates data transfer by establishing a start
condition, defined as a high-to-low transition on the serial
data line SDA, while the serial clock line, SCL, remains high.
This indicates that an address/data stream follows. All slave
peripherals connected to the serial bus responds to the start
condition and shift in the next eight bits, consisting of a
7-bit address (MSB first) plus an R/ W bit that determines the
direction of the data transfer, that is, whether data is written to
or read from the slave device.
The peripheral whose address corresponds to the transmitted
address responds by pulling the data line low during the low
period before the ninth clock pulse, known as the acknowledge
bit. All other devices on the bus remain idle while the selected
device waits for data to be read from or written to it. If the R/ W
bit is a 0, the master writes to the slave device. If the R/ W bit is a
1, the master reads from the slave device.
2
C-compatible devices, the AD7997/AD7998 have a
DD
, or by letting the pin float (see Table 6). By giving
2
C addresses available,
2
C-
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Data is sent over the serial bus in sequences of nine clock
pulses, eight bits of data followed by an acknowledge bit from
the receiver of data. Transitions on the data line must occur
during the low period of the clock signal and remain stable
during the high period because a low-to-high transition when
the clock is high may be interpreted as a stop signal.
When all data bytes have been read or written, stop conditions
are established. In write mode, the master pulls the data line
high during the 10th clock pulse to assert a stop condition. In
read mode, the master device pulls the data line high during the
low period before the ninth clock pulse. This is known as No
Acknowledge. The master then takes the data line low during
the low period before the 10th clock pulse, then high during the
10th clock pulse to assert a stop condition.
Any number of bytes of data may be transferred over the serial
bus in one operation, but it is not possible to mix read and write
in one operation, because the type of operation is determined at
the beginning and cannot subsequently be changed without
starting a new operation.
AD7997/AD7998