adt7476a Analog Devices, Inc., adt7476a Datasheet - Page 14

• Manufacturer Part Number: adt7476a
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADT7476A
WRITE OPERATIONS
The SMBus specification defines several protocols for different
types of read and write operations. The ones used in the
ADT7476A are discussed below. The following abbreviations
are used in the diagrams:
•
•
•
•
•
•
The ADT7476A uses the following SMBus write protocols.
Send Byte
In this operation, the master device sends a single command
byte to a slave device, as follows:
1.
2.
3.
4.
5.
6.
For the ADT7476A, the send byte protocol is used to write a
register address to RAM for a subsequent single-byte read
from the same address. This operation is illustrated in Figure 21.
If the master is required to read data from the register
immediately after setting up the address, it can assert a
repeat start condition immediately after the final ACK
and carry out a single byte read without asserting an
intermediate stop condition.
S – START
P – STOP
R – READ
W – WRITE
A – ACKNOWLEDGE
A – NO ACKNOWLEDGE
The master device asserts a start condition on SDA.
The master sends the 7-bit slave address followed by
the write bit (low).
The addressed slave device asserts ACK on SDA.
The master sends a command code.
The slave asserts ACK on SDA.
The master asserts a stop condition on SDA, and the
transaction ends.
Figure 21. Setting a Register Address for Subsequent Read
S
1
ADDRESS
SLAVE
2
W A
3
REGISTER
ADDRESS
4
A
5
6
P
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Write Byte
In this operation, the master device sends a command byte and
one data byte to the slave device, as follows:
1.
2.
3.
4.
5.
6.
7.
8.
This operation is illustrated in Figure 22.
READ OPERATIONS
The ADT7476A uses the following SMBus read protocols.
Receive Byte
This operation is useful when repeatedly reading a single register.
The register address is set up beforehand. In this operation, the
master device receives a single byte from a slave device, as follows:
1.
2.
3.
4.
5.
6.
In the ADT7476A, the receive byte protocol is used to read a
single byte of data from a register whose address has previously
been set by a send byte or write byte operation. This operation
is illustrated in Figure 23.
The master device asserts a start condition on SDA.
The master sends the 7-bit slave address followed by
the write bit (low).
The addressed slave device asserts ACK on SDA.
The master sends a command code.
The slave asserts ACK on SDA.
The master sends a data byte.
The slave asserts ACK on SDA.
The master asserts a stop condition on SDA,
and the transaction ends.
The master device asserts a start condition on SDA.
The master sends the 7-bit slave address followed by the
read bit (high).
The addressed slave device asserts ACK on SDA.
The master receives a data byte.
The master asserts NO ACK on SDA.
The master asserts a stop condition on SDA, and the
transaction ends.
S
1
ADDRESS W A
SLAVE
Figure 23. Single-Byte Read from a Register
Figure 22. Single-Byte Write to a Register
2
S
1
ADDRESS
SLAVE
2
3
REGISTER
ADDRESS
R
A
3
4
DATA
4
A
5
DATA
A
5
6
P
6
A P
7 8