ADT7467 Analog Devices, Inc., ADT7467 Datasheet - Page 13

• Manufacturer Part Number: ADT7467
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

WRITE OPERATIONS
The SMBus specification defines several protocols for different
types of read and write operations. The ones used in the
ADT7467 are discussed below. The following abbreviations are
used in Figure 19 through Figure 21:
S = start
P = stop
R =read
W = write
A = acknowledge
A = no acknowledge
The ADT7467 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 ADT7467, 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 19.
If the master is required to read data from the register directly
after setting up the address, it can assert a repeat start condition
immediately after the final acknowledge and carry out a single
byte read without asserting an intermediate stop condition.
Write Byte
In this operation, the master device sends a command byte and
one data byte to the slave device as follows:
1.
2.
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 an acknowledge on SDA.
The master sends a command code.
The slave asserts an acknowledge 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
write bit (low).
Figure 19. Setting a Register Address for Subsequent Read
1
S
ADDRESS
SLAVE
2
W A
3
REGISTER
ADDRESS
4
5
A
P
6
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3.
4.
5.
6.
7.
8.
This operation is illustrated in Figure 20.
READ OPERATIONS
The ADT7467 uses the following SMBus read protocols.
Receive Byte
This operation is useful when repeatedly reading a single
register. The register address must have been set up previously.
In this operation, the master device receives a single byte from a
slave device as follows:
1.
2.
3.
4.
5.
6.
In the ADT7467, 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 21.
The addressed slave device asserts an acknowledge on SDA.
The master sends a command code.
The slave asserts an acknowledge on SDA.
The master sends a data byte.
The slave asserts an acknowledge on SDA.
The master asserts a stop condition on SDA to end the
transaction.
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 an acknowledge on SDA.
The master receives a data byte.
The master asserts a no acknowledge on SDA.
The master asserts a stop condition on SDA, and the
transaction ends.
S
1
ADDRESS
Figure 21. Single Byte Read from a Register
SLAVE
Figure 20. Single Byte Write to a Register
2
1
S
ADDRESS
SLAVE
W
2
3
A
ADDRESS
R A
SLAVE
3
4
DATA
4
A
5
A P
5
DATA
6
6
A
7
P
8
ADT7467