7.4.1 Pointer register

 

The Pointer register contains an 8-bit data byte, of which the two LSB bits represent the

pointer value of the other four registers, and the other 6 MSB bits are equal to 0, as shown

in Table 6 and Table 7. The Pointer register is not accessible to the user, but is used to

select the data register for write/read operation by including the pointer data byte in the

bus command.

 

Table 6.

Pointer register

B7

B6

B5

B4

B3

B2

B[1:0]

0

0

0

0

0

0

pointer value

 

 

Table 7.

Pointer value

B1

B0

Selected register

0

0

Temperature register (Temp)

0

1

Configuration register (Conf)

1

0

Hysteresis register (Thyst)

1

1

Overtemperature shutdown register (Tos)

 

Because the Pointer value is latched into the Pointer register when the bus command

(which includes the pointer byte) is executed, a read from the LM75B may or may not

include the pointer byte in the statement. To read again a register that has been recently

read and the pointer has been preset, the pointer byte does not have to be included. To

read a register that is different from the one that has been recently read, the pointer byte

must be included. However, a write to the LM75B must always include the pointer byte

in the statement. The bus communication protocols are described in Section 7.10.

 

At power-up, the Pointer value is equal to 00 and the Temp register is selected; users can

then read the Temp data without specifying the pointer byte.

 

7.4.2 Configuration register

 

The Configuration register (Conf) is a write/read register and contains an 8-bit

non-complement data byte that is used to configure the device for different operation

conditions. Table 8 shows the bit assignments of this register.

 

Table 8.

Conf register

Legend: * = default value.

Bit

Symbol

Access Value Description

B[7:5]

reserved

R/W

000*

reserved for manufacturer’s use; should be kept as

zeroes for normal operation

B[4:3]

OS_F_QUE[1:0] R/W

OS fault queue programming

00*

queue value = 1

01

queue value = 2

10

queue value = 4

11

queue value = 6

B2

OS_POL

R/W

OS polarity selection

0*

OS active LOW

1

OS active HIGH

 

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