Data Sheet

ADT7420

Rev. 0 | Page 13 of 24

REGISTERS

The ADT7420 contains 14 registers:

•

Nine temperature registers

•

A status register

•

An ID register

•

A configuration register

•

An address pointer register

•

A software reset

All registers are eight bits wide. The temperature value registers,

the status register, and the ID register are read-only. The software

reset is a write-only register. On power-up, the address pointer

register is loaded with 0x00 and points to the temperature value

most significant byte register (Register Address 0x00).

Table 6. ADT7420 Registers

Register

Address

Description

Power-On

Default

0x00

Temperature value most significant byte

0x00

0x01

Temperature value least significant byte

0x00

0x02

Status

0x00

0x03

Configuration

0x00

0x04

0x20 (64°C)

0x05

0x00 (64°C)

0x06

0x05 (10°C)

0x07

0x00 (10°C)

0x08

0x49 (147°C)

0x09

0x80 (147°C)

0x0A

0x05 (5°C)

0x0B

ID

0xCB

0x2F

Software reset

0xXX

ADDRESS POINTER REGISTER

This register is always the first register written to during a write

to the ADT7420. It should be set to the address of the register

to which the write or read transaction is intended. Table 7

shows the register address of each register on the ADT7420.

The default value of the address pointer register is 0x00.

Table 7. Address Pointer Register

P7

P6

P5

P4

P3

P2

P1

P0

ADD7

ADD6

ADD5

ADD4

ADD3

ADD2

ADD1

ADD0

TEMPERATURE VALUE REGISTERS

The temperature value consists of two bytes, one most signifi-

cant byte and one least significant byte. These values can be

read in two separate 1-byte reads or in a single 2-byte read. For a

2-byte read, only the address of the most significant byte must be

loaded into the address pointer register. After the most signifi-

cant byte is read, the address pointer is auto-incremented so that

the least significant byte can read within the same transaction.

the ADC is configured to convert the temperature to a 16-bit

digital value, then Bit 0 to Bit 2 are no longer used as flag bits

and are instead used as the LSBs for the extended digital value.

Table 8. Temperature Value MSB Register (Register Address 0x00)

Bit

Default Value

Type

Name

Description

[14:8]

0000000

R

Temp

Temperature value in twos complement format

15

0

R

Sign

Sign bit, indicates if the temperature value is negative or positive

Table 9. Temperature Value LSB Register (Register Address 0x01)

Bit

Default

Value

Type

Name

Description

0

0

R

Contains the Least Significant Bit 0 of the 15-bit temperature value if the configuration

register, Register Address 0x03[7] = 1 (16-bit resolution).

1

0

R

Contains the Least Significant Bit 1 of the 15-bit temperature value if the configuration

register, Register Address 0x03[7] = 1 (16-bit resolution).

2

0

R

Contains the Least Significant Bit 2 of the 15-bit temperature value if the configuration

register, Register Address 0x03[7] = 1 (16-bit resolution).

[7:3]

00000

R

Temp

Temperature value in twos complement format.