ADM1034ARQZ datasheet(12/39 Pages) ONSEMI

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ADM1034

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Write Operations

The SMBus specifications define protocols for read and

write operations. The ADM1034 supports send byte, write

byte, and block byte SMBus write protocols. The following

abbreviations are used in the diagrams:

S—START

P—STOP

R—READ

W—WRITE

A—ACKNOWLEDGE

A—NO ACKNOWLEDGE

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 a 7−bit 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 asserts a stop condition on SDA, and

the transaction ends.

Figure 20. Send Byte

SLAVE

ADDRESS

REG

ADDRESS

W A

A P

The ADM1034 uses the send byte operation to write a

same address. (See Figure 24.) The user may be required to

read data from the register immediately after setting up the

address. If so, 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 register

address and one data byte to the slave device as follows:

1. The master asserts a start condition on SDA.

2. The master sends the 7−bit slave address followed

by a write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends the register address. The MSB of

the register address should equal 0 for a write byte

operation. If the MSB equals 1, a block write

operation takes place.

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.

Figure 21. Write Byte Operation

SLAVE

ADDRESS

REG

ADDRESS

DATA

W A

Block Write

In this operation, the master device writes a block of data

to a slave address as follows. A maximum of 32 bytes can be

written.

1. The master asserts a start condition on SDA.

2. The master sends the 7−bit slave address followed

by a write bit (low).

3. The addressed slave device asserts ACK on SDA.

4. The master sends the register address. The register

address sets up the address pointer register and

determines whether a block write (MSB = 1) or a

byte write (MSB = 0) takes place.

5. The slave asserts ACK on SDA.

6. The master sends the byte count.

7. The slave asserts ACK on SDA.

8. The master sends N data bytes.

9. The slave asserts ACK on SDA after each byte.

10. The master asserts a stop condition on SDA to end

the transaction.

Figure 22. Block Write to RAM

SLAVE

ADDRESS

BYTE

COUNT

DATA 2

DATA 1

ADDRESS

W A

A P

ADATA N

Read Operations

Receive Byte

This is useful when repeatedly reading a single register.

The register address must be set up prior to this, with the

MSB at 0 to read a single byte. 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 sends NO ACK on SDA.

6. The master asserts a stop condition on SDA, and

the transaction ends.

In the ADM1034, the receive byte protocol is used to read

a single byte from a register whose address has previously

been set by a send byte or write byte operation.

Figure 23. Receive Byte

SLAVE

ADDRESS

DATA

R A

A P

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