Data Sheet

ADT7420

Rev. 0 | Page 19 of 24

READING DATA

Reading data from the ADT7420 is done in a single data byte

operation for the configuration register, the status register,

read operation is needed for the temperature value register,

setpoint register. Reading back the contents of an 8-bit register

similar to the configuration register is shown in Figure 16.

Reading back the contents of the temperature value register

is shown in Figure 17.

Reading back from any register first requires a single-byte write

operation to the address pointer register to set up the address of

the register that is going to be read from. In the case of reading

back from the 2-byte registers, the address pointer automatically

increments from the MSB register address to the LSB register

address.

To read from another register, execute another write to the

address pointer register to set up the relevant register address.

pointer auto-increment except when reading back from a 16-bit

register. If the address pointer register has previously been set

up with the address of the register that is going to receive a read

command, there is no need to repeat a write operation to set up

the register address again.

SCL

SDA

1

10

0

1

A1

0A0

REPEAT START

BY MASTER

FRAME 3

SERIAL BUS ADDRESS

BYTE

FRAME 4

DATA BYTE FROM CONFIGURATION

REGISTER

STOP BY

MASTER

ACK. BY

ADT7420

NO ACK. BY

MASTER

R/W

D7

D6

D5

D4D3D2

D1

D0

99

1

SCL

SDA

1

10

0

1

A1

A0

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS

BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

ACK. BY

ADT7420

ACK. BY

ADT7420

R/W

P7

P6

P5

P4P3

P2

P1P0

99

1

0

Figure 16. Reading Back Data from the Configuration Register

NOTES

1. A START CONDITION AT THE BEGINNING IS DEFINED AS A HIGH-TO-LOW TRANSITION ON SDA WHILE SCL REMAINS HIGH.

2. A STOP CONDITION AT THE END IS DEFINED AS A LOW-TO-HIGH TRANSITION ON SDA WHILE SCL REMAINS HIGH.

3. THE MASTER GENERATES THE NO ACKNOWLEDGE AT THE END OF THE READBACK TO SIGNAL THAT IT DOES NOT WANT ADDITIONAL DATA.

4. TEMPERATURE VALUE REGISTER MSB DATA AND TEMPERATURE VALIUE REGISTER LSB DATA ARE ALWAYS SEPARATED BY A LOW ACK BIT.

5. THE R/W BIT IS SET TO A1 TO INDICATE A READBACK OPERATION.

SDA

10

0

R/W

A7

A6

SCL

SDA

SCL

1

A1

A0

11

0A1

A0

9

ADT7410 DEVICE ADDRESS

REGISTER ADDRESS[A7:A0]

D1

D0

D7

D6

TEMPERATURE

VALUE REGISTER

MSB DATA

9

1

1

9

9

0

1A1

A0

R/W

REPEAT

START

D1

D0

D7

D6

ACK. BY

ADT7420

ACK. BY

MASTER

NO

ACK. BY

MASTER

ACK. BY

ADT7420

START

ADT7410 DEVICE ADDRESS

ACK. BY

ADT7420

TEMPERATURE

VALUE REGISTER

LSB DATA

SR

Figure 17. Reading Back Data from the Temperature Value Register