ADT7481

Rev. 0 | Page 12 of 24

REGISTERS

The registers in the ADT7481 are eight bits wide. These

registers are used to store the results of remote and local

temperature measurements, high and low temperature limits,

and to configure and control the device. A description of these

registers follows.

ADDRESS POINTER REGISTER

The address pointer register does not have, nor does it require,

an address because the first byte of every write operation is

automatically written to this register. The data in this first byte

always contains the address of another register on the ADT7481,

which is stored in the address pointer register. It is to this register

address that the second byte of a write operation is written to, or

to which a subsequent read operation is performed.

The power-on default value of the address pointer register is

0x00, so if a read operation is performed immediately after

power-on, without first writing to the address pointer, the value

of the local temperature will be returned since its register

address is 0x00.

TEMPERATURE VALUE REGISTERS

The ADT7481 has five registers to store the results of local and

remote temperature measurements. These registers can only be

written to by the ADC and read by the user over the SMBus.

• The local temperature value register is at Address 0x00.

• The Remote 1 temperature value high byte register is at

Address 0x01, with the Remote 1 low byte register at

Address 0×10.

• The Remote 2 temperature value high byte register is at

Address 0x30, with the Remote 2 low byte register at

Address 0x33.

• The Remote 2 temperature values can also be read from

Address 0x01 for the high byte, and Address 0x10 for the low

byte if Bit 3 of Configuration Register 1 is set to 1.

• To read the Remote 1 temperature values, set Bit 3 of

Configuration Register 1 to 0.

• The power-on default value for all five registers is 0x00.

Table 8: Configuration 1 Register

(Read Address 0x03, Write Address 0x09)

Bit

Mnemonic

Function

7

Mask

Setting this bit to 1 masks all ALERTs on the ALERT pin. Default = 0 = ALERT enabled. This applies only if Pin 8 is

configured as ALERT, otherwise it has no effect.

6

Mon/STBY

Setting this bit to 1 places the ADT7481 in standby mode, that is, it suspends all temperature measurements (ADC).

The SMBus remains active and values can be written to, and read from, the registers. However THERM and ALERT are

not active in standby mode, and their states in standby mode are not reliable. Default = 0 = temperature monitoring

enabled.

5

AL/TH

This bit selects the function of Pin 8. Default = 0 = ALERT. Setting this bit to 1 configures Pin 8 as the THERM2 pin.

4

Reserved

Reserved for future use.

3

Remote 1/2

Setting this bit to 1 enables the user to read the Remote 2 values from the Remote 1 registers. When default = 0,

Remote 1 temperature values and limits are read from these registers.

2

Temp Range

Setting this bit to 1 enables the extended temperature measurement range of −64°C to +191°C. When using the

default = 0, the temperature range is 0°C to +127°C.

1

Mask R1

Setting this bit to 1 masks ALERTs due to the Remote 1 temperature exceeding a programmed limit. Default = 0.

0

Mask R2

Setting this bit to 1 masks ALERTs due to the Remote 2 temperature exceeding a programmed limit. Default = 0.

Table 9. Configuration 2 Register (Address 0x24)

Bit

Mnemonic

Function

7

Lock Bit

Setting this bit to 1 locks all lockable registers to their current values. This prevents tampering with settings until

the device is powered down. Default = 0.

<6:0>

Res

Reserved for future use.