ADT7460ARQ-REEL ON Semiconductor, ADT7460ARQ-REEL Datasheet - Page 13

• Manufacturer Part Number: ADT7460ARQ-REEL
• Description: IC SENSOR TEMP FAN-CTRL 16QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7460ARQ-REEL

• Rohs Status: RoHS non-compliant
• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 120°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP

When reading data from a register, there are two possibilities:
•
•
It is possible to read a data byte from a data register without first
writing to the address pointer register if the address pointer
register is already at the correct value. However, it is not possible
to write data to a register without writing to the address pointer
register because the first data byte of a write is always written to
the address pointer register.
In Figure 18 to Figure 20, the serial bus address is shown as the
default value 01011(A1)(A0), where A1 and A0 are set by the
address select mode function previously defined.
In addition to supporting the Send Byte and Receive Byte
protocols, the ADT7460 also supports the Read Byte protocol
(see System Management Bus specifications Rev. 2.0 for more
information).
If the ADT7460’s address pointer register value is unknown
or not the desired value, it is first necessary to set it to the
correct value before data can be read from the desired data
register. This is done by performing a write to the ADT7460
as before, but only the data byte containing the register
address is sent because data is not to be written to the
register. This is shown in Figure 19.
A read operation is then performed, consisting of the serial
bus address, R/ W bit set to 1, followed by the data byte
read from the data register. This is shown in Figure 20.
If the address pointer register is known to be already at the
desired address, data can be read from the corresponding
data register without first writing to the address pointer
register, so Figure 19 can be omitted.
SDA
SCL
SDA
SCL
START BY
MASTER
START BY
MASTER
1
0
1
0
1
1
0
SERIAL BUS ADDRESS
0
SERIAL BUS ADDRESS
1
FRAME 1
1
FRAME 1
BYTE
BYTE
1
1
Figure 20. Read
Figure 19. Writing to the Address Pointer Register Only
A1
A1
A0
A0
ing Data from a Previously Selected Register
R/W
R/
W
Rev. C | Page 13 of 52
ADT7460
ADT7460
ACK. BY
ACK
. BY
9
9
D7
D7
1
1
If it is required to perform several read or write operations in
succession, the master can send a repeat start condition instead
of a stop condition to begin a new operation.
Write Operations
The SMBus specification defines several protocols for different
types of read and write operations. The ones used in the
ADT7460 are discussed below. The following abbreviations are
used in the diagrams:
S—start
P—stop
R—read
W—write
A—acknowledge
A —no acknowledge
The ADT7460 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.
D6
D6
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 the register address.
The slave asserts ACK on SDA.
The master asserts a stop condition on SDA and the
transaction ends.
ADDRESS POINTER REGISTER BYTE
D5
D5
DATA BYTE FROM ADT7460
D4
D4
FRAME 2
FRAME 2
D3
D3
D2
D2
D1
D1
D0
D0
NO ACK. BY
MASTER
ADT7460
ACK. BY
9
9
STOP BY
MASTER
STOP BY
MASTER
ADT7460