ADT7420

Preliminary Technical Data

Rev. PrA | Page 18 of

WRITING DATA

It is possible to write either a single byte of data or two bytes to

the ADT7420, depending on which registers are to be written.

Writing a single byte of data requires the serial bus address, the

data register address written to the address pointer register,

followed by the data byte written to the selected data register.

This is shown in Figure 14.

it is possible to write to both the MSB and the LSB registers in

the same write transaction. Writing two bytes of data to these

registers requires the serial bus address, the data register address

of the MSB register written to the address pointer register,

followed by the two data bytes written to the selected data

register. This is shown in Figure 15.

If more than the required number of data bytes is written to a

register, the register ignores these extra data bytes. To write to

a different register, a start or repeated start is required.

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

ACK. BY

ADT7420

ACK. BY

ADT7420

ACK. BY

ADT7420

STOP BY

MASTER

FRAME 3

DATA BYTE

SDA (CONTINUED)

SCL (CONTINUED)

SCL

SDA

START BY

MASTER

1

0

0

1

0

A1

A0

P7

P6

P5

P4

P3

P2

P1

P0

9

D7

D6

D5

D4

D3

D2

D1

D0

R/W

1

9

1

9

1

Figure 14. Writing to a Register Followed by a Single Byte of Data

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

ACK. BY

ADT7420

ACK. BY

ADT7420

ACK. BY

ADT7420

STOP BY

MASTER

FRAME 4

DATA BYTE

SCL

SDA

START BY

MASTER

1

0

0

1

0

A1

A0

P7

P6

P5

P4

P3

P2

P1

P0

9

D7

D6

D5

D4

D3

D2

D1

D0

R/W

1

9

1

9

1

ACK. BY

ADT7420

FRAME 3

DATA BYTE

SDA (CONTINUED)

SCL (CONTINUED)

D15

D14

D13

D12

D11

D10

D9

D8

9

1

Figure 15. Writing to a Register Followed by Two Bytes of Data