ADT7483A

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write operation contains a second data byte that is written to the

register selected by the address pointer register (see Figure 16).

The device address is sent over the bus followed by R/W set

to 0. This is followed by two data bytes. The first data byte is

the address of the internal data register to be written to, which

is stored in the address pointer register. The second data byte is

the data to be written to the internal data register.

D7

D6

D5

D4

D3

D2

D1

D0

FRAME 3

DATA

BYTE

ACK. BY

ADT7483A

STOP BY

MASTER

SDA (CONTINUED)

SCL (CONTINUED)

FRAME 1

SERIAL BUS ADDRESS BYTE

ACK. BY

ADT7483A

SDA

SCL

START BY

MASTER

FRAME 2

ADDRESS POINTER REGISTER BYTE

D7

D6

D5

D4

D3

D2

D1

D0

1

00

1

1

01

R/W

ACK. BY

ADT7483A

1

1

9

9

1

9

Figure 16. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register

FRAME 1

SERIAL BUS ADDRESS BYTE

ACK. BY

ADT7483A

SDA

SCL

START BY

MASTER

FRAME 2

ADDRESS POINTER REGISTER BYTE

D7

D6

D5

D4

D3

D2

D1

D0

10

0

1

1

0

1

R/W

ACK. BY

ADT7483A

1

1

9

9

STOP BY

MASTER

Figure 17. Writing to the Address Pointer Register Only

FRAME 1

SERIAL BUS ADDRESS BYTE

ACK. BY

ADT7483A

SDA

SCL

START BY

MASTER

FRAME 2

DATA BYTE FROM ADT7483A

D7

D6

D5

D4

D3

D2

D1

D0

10

0

1

1

0

1

R/W

ACK. BY

MASTER

1

1

9

9

STOP BY

MASTER

Figure 18. Reading from a Previously Selected Register

When reading data from a register there are two possibilities:

•

If the address pointer register value of the ADT7483A is

unknown or not the desired value, it is first necessary to set

it to the correct value before data can be read from the

desired data register. This is done by performing a write to

the ADT7483A as before, but only the data byte containing

the register read address is sent, as data is not to be written

to the register (see Figure 17).

A read operation is then performed consisting of the serial

bus address, R/W bit set to 1, followed by the data byte

read from the data register (see Figure 18).

•

If the address pointer register is known to be already at the

desired address, data can be read from the corresponding

data register without first writing to the address pointer

register and the bus transaction shown in Figure 17 can

be omitted.