ADT7460(2013) データシートの表示（PDF） - ON Semiconductor
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ADT7460 Datasheet PDF : 47 Pages
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1
SCL
ADT7460
9
1
9
SDA
0
START BY
MASTER
1
0
1
1 A1 A0
FRAME 1
SERIAL BUS ADDRESS BYTE
R/W
D7
ACK. BY
ADT7460
D6 D5 D4 D3 D2 D1 D0
FRAME 2
ADDRESS POINTER REGISTER BYTE
ACK. BY
ADT7460
STOP BY
MASTER
Figure 18. Writing to the Address Pointer Register Only
1
9
1
9
SCL
SDA
0
START BY
MASTER
1
0
1
1
A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
FRAME 1
SERIAL BUS ADDRESS BYTE
ACK. BY
ADT7460
FRAME 2
DATA BYTE FROM ADT7460
NO ACK. BY STOP BY
MASTER MASTER
Figure 19. Reading Data from a Previously Selected Register
For the ADT7460, the send byte protocol is used to write
to the address pointer register for a subsequent single-byte
read from the same address. This is illustrated in Figure 20.
1
2
3
4
56
S
SLAVE
ADDRESS
W
A
REGISTER
ADDRESS
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 condition 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 the 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 illustrated 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 ADT7460 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.
In the ADT7460, 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 by write byte operation.
1
2
3
S
SLAVE
ADDRESS
R
A
4
DATA
56
AP
Figure 22. Single-Byte Read from a Register
Alert Response Address
Alert response address (ARA) is a feature of SMBus
devices that allows an interrupting device to identify itself
to the host when multiple devices exist on the same bus.
The SMBALERT output can be used as an interrupt
output or can be used as an SMBALERT. One or more
outputs can be connected to a common SMBALERT line
connected to the master. If a device’s SMBALERT line goes
low, the following occurs:
1. SMBALERT is pulled low.
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