DS18B20

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Figure 2. Temperature Register Format

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

LS BYTE

2

3

2

2

2

1

2

0

2

-1

2

-2

2

-3

2

-4

BIT 15

BIT 14

BIT 13

BIT 12

BIT 11

BIT 10

BIT 9

BIT 8

MS BYTE

S

S

S

S

S

2

6

2

5

2

4

S = SIGN

Table 1. Temperature/Data Relationship

TEMPERATURE (

°C)

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

+125

0000 0111 1101 0000

07D0h

+85*

0000 0101 0101 0000

0550h

+25.0625

0000 0001 1001 0001

0191h

+10.125

0000 0000 1010 0010

00A2h

+0.5

0000 0000 0000 1000

0008h

0

0000 0000 0000 0000

0000h

-0.5

1111 1111 1111 1000

FFF8h

-10.125

1111 1111 0101 1110

FF5Eh

-25.0625

1111 1110 0110 1111

FE6Fh

-55

1111 1100 1001 0000

FC90h

*The power-on reset value of the temperature register is +85°C.

OPERATION—ALARM SIGNALING

After the DS18B20 performs a temperature conversion, the temperature value is compared to the user-

The sign bit (S) indicates if the value is positive or negative: for positive numbers S = 0 and for negative

in the Memory section.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

S

2

6

2

5

2

4

2

3

2

2

2

1

2

0

an alarm condition exists and an alarm flag is set inside the DS18B20. This flag is updated after every

temperature measurement; therefore, if the alarm condition goes away, the flag will be turned off after the

next temperature conversion.