ADT7462ACPZ-R7 datasheet(17/81 Pages) ONSEMI

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ADT7462

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For the ADT7462, the send byte protocol is used to write

a register address to RAM for a subsequent single byte read

from the same address. This operation is shown in Figure 27.

Figure 27. Setting a Register Address for

Subsequent Read

SLAVE

ADDRESS

SA P

ADDRESS

15 6

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 an ACK on SDA.

4. The master sends a command code.

5. The slave asserts an ACK on SDA.

6. The master sends a data byte.

7. The slave asserts an ACK on SDA.

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

the transaction.

Figure 28. Single−Byte Write to a Register

SLAVE

ADDRESS W A

DATA

A P

SLAVE

ADDRESS

7 8

Block Write

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

to a slave device. The start address for a block write must be

set previously. In the case of the ADT7462, this is done by

a send byte operation to set a RAM address. The user writes

the number of registers to be written to in the block read

command to the #Bytes bits of the Configuration 0 register.

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 an ACK on SDA.

4. The master sends a command code that tells the

slave device to expect a block write. The

ADT7462 command code for a block write is

0xA0 (1010 0000).

5. The slave asserts an ACK on SDA.

6. The master sends the data bytes (the number of

data bytes sent is written to the #Bytes bits of the

Configuration 0 register).

7. The slave asserts an ACK on SDA after each data

byte.

8. The master sends a packet error checking (PEC) byte.

9. The ADT7462 checks the PEC byte and issues an

ACK, if correct. If incorrect (NO ACK), the

master resends the data bytes.

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

the transaction.

Figure 29. Block Write to ADT7462

SW A

ADATA 1 AA

DATA 2 A DATA

PEC

SLAVE

ADDRESS

COMMAND

0xA0

BLOCK

WRITE

BYTE

COUNT

10 11 12

Read Operations

The ADT7462 uses the following SMBus read protocols.

Receive Byte

The receive byte is useful when repeatedly reading a

single register. The register address must be 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 an ACK on SDA.

4. The master receives a data byte.

5. The master asserts a NO ACK on SDA.

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

the transaction.

For the ADT7462, 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 a byte operation.

Figure 30. Single−Byte Read from a Register

SLAVE

ADDRESS

DATA

SA P

15 6

Block Read

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

from a slave device. The start address for a block read must

be set previously, as well as the number of bytes to be read

(maximum = 32). In the case of the ADT7462, the start

address is activated by a send byte operation to set a RAM

address. The number of bytes to be read should be written to

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