Preliminary Technical Data

ADT7420

Rev. PrA | Page 19 of

READING DATA

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

operation for the configuration register, the status 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 autoincrement 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.

RESET

an explicit reset command is provided. This uses a particular

address pointer word as a command word to reset the part and

upload all default settings. The ADT7420 does not respond to

values upload for approximately 200 µs.

The reset command address word is 0x2F.

GENERAL CALL

When a master issues a slave address consisting of seven 0s with

the eighth bit (R/W

The ADT7420 does not acknowledge any other general call

commands.

bit) set to 0, this is known as the general call

address. The general call address is for addressing every device

and reads in the following data byte.

If the second byte is 0x06, the ADT7420 is reset, completely

uploading all default values. The ADT7420 does not respond

default values upload for approximately 200 µs.

SCL

SDA

1

1

0

0

1

A1

0

A0

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

D4

D3

D2

D1

D0

9

9

1

SCL

SDA

1

1

0

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

P4

P3

P2

P1

P0

9

9

1

0

Figure 16. Reading Back Data from the Configuration Register