ADT7516/ADT7517/ADT7519
I2C Serial Interface
2. 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 can be interpreted as a
stop signal.
Like all I2C-compatible devices, the ADT7516/ADT7517/
ADT7519 have a 7-bit serial address. The four MSBs of this
address for the ADT7516/ADT7517/ADT7519 are set to 1001.
The three LSBs are set by Pin 11, ADD. The ADD pin can be
configured three ways to give three different address options:
low, floating, and high. Setting the ADD pin low gives a serial bus
address of 1001 000, leaving it floating gives the Address 1001 010,
and setting it high gives the Address 1001 011. The recommended
pull-up resistor value is 10 kΩ.
3. 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, and then high during the 10th clock pulse to
assert a stop condition.
There is an enable/disable bit for the SMBus timeout. When this
is enabled, the SMBus times out after 25 ms of no activity. To
enable it, set Bit 6 of the Control Configuration 2 register. The
power-on default is with the SMBus timeout disabled.
The ADT7516/ADT7517/ADT7519 support SMBus packet
error checking (PEC), but its use is optional. It is triggered by
supplying the extra clocks for the PEC byte. The PEC is
calculated using CRC-8. The frame clock sequence (FCS)
conforms to CRC-8 by the polynomial
Any number of bytes of data can 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.
C(x) = x8 + x2 + x1 + 1
Consult the SMBus specification for more information.
The serial bus protocol operates as follows:
The I2C address set up by the ADD pin is not latched by the
device until after this address has been sent twice. On the eighth
SCL cycle of the second valid communication, the serial bus
address is latched in. This is the SCL cycle directly after the
device has seen its own I2C serial bus address. Any subsequent
changes on this pin have no effect on the I2C serial bus address.
1. The master initiates a 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 respond to
the start condition and shift in the next eight bits,
Writing to the ADT7516/ADT7517/ADT7519
Depending on the register being written to, there are two different
writes for the ADT7516/ADT7517/ADT7519. It is not possible
to do a block write to this part, that is, no I2C auto-increment.
W
consisting of a 7-bit address (MSB first) plus a R/ bit; this
determines the direction of the data transfer, that is,
whether data is written to or read from the slave device.
Writing to the Address Pointer Register for a
Subsequent Read
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 now
remain idle while the selected device waits for data to be
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 60. 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 is then performed
to read the register.
W
read from or written to it. If the R/ bit is 0, the master
W
writes to the slave device. If the R/ bit is 1, the master
reads from the slave device.
1
9
1
9
SCL
1
0
0
1
A2
A1
A0
R/W
ACK. BY
P7
P6
P5
P4
P3
P2
P1
P0
SDA
START BY
ACK. BY
ADT7516/ADT7517/ADT7519 MASTER
STOP BY
MASTER
ADT7516/ADT7517/ADT7519
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
Figure 60. I2C—Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation
Rev. B | Page 38 of 44
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