ADT7467 データシートの表示（PDF） - ON Semiconductor

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ADT7467

dbCOOL Remote Thermal Monitor and Fan Controller

ON Semiconductor 

ADT7467

In the ADT7467, write operations contain either one or

two bytes, and read operations contain one byte. To write

data to a device data register or read data from it, the address

pointer register must first be set. The first byte of a write

operation always contains an address, which is stored in the

address pointer register, and the second byte, if there is a

second byte, is written to the register selected by the address

pointer register.

This write operation is illustrated in Figure 15. The device

address is sent over the bus, and then R/W is set to 0. This

is followed by two data bytes. The first data byte is the

address of the internal data register, and the second data byte

is the data written to that internal data register.

When reading data from a register, there are two

possibilities:

1. If the address pointer register value of the

ADT7467 is unknown or not the desired value, it

must be set to the correct value before data can be

read from the desired data register. This is

achieved by writing a data byte containing the

register address to the ADT7467. This is shown in

Figure 16. A read operation is then performed

1

9

SCL

consisting of the serial bus address and the R/W

bit set to 1, followed by the data byte read from

the data register. This is shown in Figure 17.

2. If the address pointer register is known to be at the

desired address, data can be read from the

corresponding data register without first writing to

the address pointer register, as shown in Figure 17.

If the address pointer register is already at the correct

value, it is possible to read a data byte from the data register

without first writing to the address pointer register.

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 addition to supporting the send byte and receive byte

protocols, the ADT7467 also supports the read byte

protocol. (See the Intel System Management Bus

Specifications Rev. 2 for more information.)

If several read or write operations must be performed in

succession, the master can send a repeat start condition

instead of a stop condition to begin a new operation.

1

9

SDA

0

START BY

MASTER

10 11 1 0

FRAME 1

SERIAL BUS ADDRESS BYTE

R/W

D7

ACK. BY

ADT7467

D6 D5 D4 D3 D2 D1 D0

ACK. BY

FRAME 2

ADT7467

ADDRESS POINTER REGISTER BYTE

1

9

SCL (CONTINUED)

SDA (CONTINUED)

D7 D6 D5 D4 D3 D2 D1 D0

FRAME 3

DATA BYTE

ACK. BY STOP BY

ADT7467 MASTER

Figure 15. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register

1

91

9

SCL

SDA

0

START BY

MASTER

1 01110

FRAME 1

SERIAL BUS ADDRESS BYTE

R/W

D7

ACK. BY

ADT7467

D6 D5 D4 D3 D2 D1 D0

ACK. BY

FRAME 2

ADT7467

ADDRESS POINTER REGISTER BYTE

STOP BY

MASTER

Figure 16. Writing to the Address Pointer Register Only

1

91

9

SCL

SDA

0

START BY

MASTER

10 11 10

FRAME 1

SERIAL BUS ADDRESS BYTE

R/W

D7

ACK. BY

ADT7467

D6 D5 D4 D3 D2 D1 D0

NO ACK. BY

FRAME 2

MASTER

DATA BYTE FROM ADT7467

STOP BY

MASTER

Figure 17. Reading Data from a Previously Selected Register

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