ADT7408

Rev. 0 | Page 19 of 24

Reading Data From the ADT7408

Reading data from the ADT7408 can take place in one of the

following two ways:

Writing to the Pointer Register for a Subsequent Read

To read data from a particular register, the pointer register must

contain the address of the data register. If it does not, the

correct address must be written to the address pointer register

by performing a single-byte write operation (see Figure 15).

The write operation consists of the serial bus address followed

by the pointer byte. No data is written to any of the data

registers. Because the location latched in the pointer register is

correct, then the read consists of an address byte, followed by

retrieving the two data bytes (see Figure 16).

Reading from Any Pointer Register

On the other hand, if the pointer register needs to be set, then

an address byte, pointer byte, repeat start, and another address

byte accomplish a read (see Figure 17).

SCL

SDA

A6

A4

A5

A3

A1

A2

A0

D7

D5

D6

D4

D2

D3

D1

D0

99

1

1

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

POINTER BYTE

ACK

BY

TS

ACK

BY

TS

STOP

BY

MASTER

START

BY MASTER

R/W

Figure 15. Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation

D7

D5

D6

D4

D2

D3

D1

D0

9

1

FRAME 3

LEAST SIGNIFICANT DATA BYTE

NO ACK

BY

MASTER

SCL

(CONTINUED)

SDA

(CONTINUED)

SCL

SDA

STOP

BY

MASTER

A6

A4

A5

A3

A1

A2

A0

R/W

D15

D13

D14

D12

D10

D11

D9

D8

99

1

1

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

MOST SIGNIFICANT DATA BYTE

ACK

BY

TS

START

BY

MASTER

ACK

BY

MASTER

Figure 16. Reading Back Data from the Register with the Preset Pointer