ADT7470

Data Sheet

Rev. E | Page 10 of 40

during the low period before the 10th clock pulse, then

high during the 10th clock pulse to assert a stop condition.

Any number of bytes of data can be transferred over the serial

bus in one operation. However, it is not possible to mix read

and write in one operation, because the type of operation is

determined at the beginning and subsequently cannot be

changed without starting a new operation.

In the ADT7470, write operations contain either one or two

bytes, and read operations contain one byte and perform the

following functions.

To write data to one of the device data registers or read data

from it, the address pointer register must be set so that the

correct data register is addressed. Then data can be written into

that register or read from it. The first byte of a write operation

always contains an address that is stored in the address pointer

register. If data is to be written to the device, the write operation

contains a second data byte that is written to the register selected

by the address pointer register.

This is illustrated in Figure 7. The device address is sent over the

bus followed by R/W set to 0. This is followed by two data bytes.

1

00

1

1

1

A1

A0

R/W

99

1

1

D7

D6

D5

D4

D3

D2

D1

D0

9

D7

D6

D5

D4

D3

D2

D1

D0

SCL

SDA

SCL (CONTINUED)

SDA (CONTINUED)

START BY

MASTER

ACK. BY

ADT7470

ACK. BY

ADT7470

ACK. BY

ADT7470

STOP BY

MASTER

FRAME 1

SERIAL BUS ADDRESS

BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

FRAME 3

DATA

BYTE

Figure 7. Writing a Register Address to the Address Pointer Register, Then Writing Data to the Selected Register

SCL

SDA

1

01

0

1

1

A1

A0

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS

BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

STOP BY

MASTER

ACK. BY

ADT7470

ACK. BY

ADT7470

R/W

D7

D6

D5

D4

D3

D2

D1

D0

99

1

Figure 8. Writing to the Address Pointer Register Only

SCL

SDA

1

01

0

1

1

A1

A0

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS

BYTE

FRAME 2

DATA BYTE FROM

ADT7470

STOP BY

MASTER

ACK. BY

ADT7470

NO ACK.

BY MASTER

R/W

D7

D6

D5

D4

D3

D2

D1

D0

99

1

Figure 9. Reading Data from a Previously Selected Register