ADT7466 Datasheet, PDF (14/48 Pages) Analog Devices – dBCool Remote Thermal Controller and Voltage Monitor

ADT7466
WRITE AND READ OPERATIONS
The SMBus specification defines several protocols for different
types of write and read operations. The protocols used in the
ADT7466 are discussed in the following sections. The following
abbreviations are used in the diagrams:
S—Start
P—Stop
R—Read
W—Write
A—Acknowledge
A—No Acknowledge
Write Operations
The ADT7466 uses the send byte and write byte protocols.
Send Byte
In this operation, the master device sends a single command
byte to a slave device, as follows:
1. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address followed by the
write bit (low).
3. The addressed slave device asserts ACK on SDA.
4. The master sends a register address.
5. The slave asserts ACK on SDA.
6. The master asserts a stop condition on SDA and the
transaction ends.
For the ADT7466, the send byte protocol is used to write a
register address to RAM for a subsequent single-byte read from
the same address. This is shown in Figure 20.
1
2
3
4
S
SLAVE
ADDRESS
WA
REGISTER
ADDRESS
56
AP
Figure 20. Setting a Register Address for Subsequent Read
If it is required to read data from the register immediately after
setting up the address, the master can assert a repeat start con-
dition immediately after the final ACK 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. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address followed by the
write bit (low).
3. The addressed slave device asserts ACK on SDA.
4. The master sends a register address.
5. The slave asserts ACK on SDA.
6. The master sends a data byte.
7. The slave asserts ACK on SDA.
8. The master asserts a stop condition on SDA to end the
transaction.
This is shown in Figure 21.
1
2
3
4
5 6 78
S
SLAVE
ADDRESS
W
A
REGISTER
ADDRESS
A DATA A P
Figure 21. Single-Byte Write to a Register
Read Operations
The ADT7466 uses the following SMBus read protocols.
Receive Byte
This is useful when repeatedly reading a single register. The
register address needs to have been set up previously.
In this operation, the master device receives a single byte from a
slave device, as follows:
1. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address followed by the
read bit (high).
3. The addressed slave device asserts ACK on SDA.
4. The master receives a data byte.
5. The master asserts NO ACK on SDA.
6. The master asserts a stop condition on SDA and the
transaction ends.
For the ADT7466, the receive byte protocol is used to read a
single byte of data from a register whose address was set
previously by a send byte or write byte operation.
1
2
3
4
S
SLAVE
ADDRESS
RA
DATA
56
AP
Rev. 0 | Page 14 of 48
Figure 22. Single-Byte Read from a Register