ADT7467ARQZ-R7 datasheet(13/77 Pages) ONSEMI

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ADT7467

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WRITE OPERATIONS

The SMBus specification defines several protocols for different

types of read and write operations. The ones used in the

ADT7467 are discussed here. 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:

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.

For the ADT7467, the send byte protocol is used to write a

the same address. This operation is illustrated in Figure 19.

SLAVE

ADDRESS

SA P

ADDRESS

15 6

Figure 19. Setting a Register Address for Subsequent Read

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:

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 sends a data byte.

The slave asserts an acknowledge on SDA.

The master asserts a stop condition on SDA to end the

transaction.

This operation is illustrated in Figure 20.

SLAVE

ADDRESS

SLAVE

ADDRESS

DATA

SA P

17 8

Figure 20. Single Byte Write to a Register

READ OPERATIONS

The ADT7467 uses the following SMBus read protocols.

Receive Byte

This operation is useful when repeatedly reading a single

In this operation, the master device receives a single byte from a

slave device as follows:

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.

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.

SLAVE

ADDRESS

SR A

A P

DATA

5 6

Figure 21. Single Byte Read from a Register

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