AD7417 AD [Analog Devices], AD7417 Datasheet - Page 12

• Manufacturer Part Number: AD7417
• Description: 10-Bit Digital Temperature Sensor (AD7416) and Single/Four-Channel ADC (AD7417/AD7418)
• Manufacturer: AD [Analog Devices]

AD7416/AD7417/AD7418
or the addresses can be set to avoid conflicts with other devices
on the bus. The four MSBs of this address for the AD7418 are set
to 0101, while the three LSBs are all set to zero.
If a serial communication occurs during a conversion operation,
the conversion will stop and will restart after the communication.
The serial bus protocol operates as follows:
1. The master initiates data transfer by establishing a start
2. Data is sent over the serial bus in sequences of nine clock
3. When all data bytes have been read or written, stop condi-
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 will follow.
All slave peripherals connected to the serial bus respond to
the 7-bit address (MSB first) plus an R/W bit, which deter-
mines the direction of the data transfer, i.e., whether data
will be 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 Acknowl-
edge bit. All other devices on the bus now 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, then the master will write to the
slave device. If the R/W bit is a 1, then the master will read
from the slave device.
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, since a low-to-high transition
when the clock is high may be interpreted as a stop signal.
tions are established. In write mode, the master will pull the
data line high during the 10th clock pulse to assert a stop
condition. In read mode, the master device will pull the data
Figure 9. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
Figure 8. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
SCL
SDA
START BY
MASTER
SDA
SCL
START BY
MASTER
1
1
1
1
0
0
SERIAL BUS ADDRESS BYTE
0
SERIAL BUS ADDRESS BYTE
0
1
FRAME 1
1
FRAME 1
A2
A2
SDA (CONTINUED)
SCL (CONTINUED)
A1
A1
A0
A0
R/W
R/W
ACK. BY
AD7416
ACK. BY
AD7416
9
–12–
D7
9
1
P7
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.
WRITING TO THE AD7416/AD7417/AD7418
Depending on the register being written to, there are three
different writes for the AD7416/AD7417/AD7418.
1. Writing to the Address Pointer Register for a subsequent read.
2. Writing a single byte of data to the configuration registers or
1
D6
P7
1
line high during the low period before the 9th clock pulse.
This is known as No Acknowledge. The master will then take
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.
In order to read data from a particular register, the Address
Pointer Register must 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 8. 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.
to the T
The Configuration Register is an 8-bit register, so only one
byte of data can be written to it. If only 8-bit temperature
comparisons are required, the temperature LSB can be
ignored in T
written to the T
Writing a single byte of data to one of these registers consists
of the serial bus address, the data register address written to
P6
D5
P6
ADDRESS POINTER REGISTER BYTE
P5
OTI
ADDRESS POINTER REGISTER BYTE
D4
P5
, T
P4
DATA BYTE
OTI
FRAME 3
HYST
D3
P4
FRAME 2
OTI
and T
P3
FRAME 2
registers.
and T
P3
D2
P2
HYST
HYST
P2
D1
, and only eight bits need be
P1
registers.
D0
P1
P0
ACK. BY
AD7416
P0
ACK. BY
9
AD7416
9
ACK. BY
AD7416
STOP BY
MASTER
9
STOP BY
MASTER
REV. G