Standard Binary to Decimal Temperature Data

Standard Decimal to Binary Temperature Data

TMP441

TMP442

SBOS425A – DECEMBER 2008 – REVISED MARCH 2009 .............................................................................................................................................. www.ti.com

Both local and remote temperature data use two

Calculation Example

bytes for data storage. The high byte stores the

temperature with 1°C resolution. The second or low

High byte conversion (for example, 0111 0011):

byte

stores

the

decimal

fraction

value

of

the

Convert the right-justified binary high byte to

temperature

and

allows

a

higher

measurement

hexadecimal.

resolution, as shown in Table 2. The measurement

From hexadecimal, multiply the first number by

resolution for both the local and remote channels is

160 = 1 and the second number by 161 = 16.

0.0625°C, and cannot be adjusted.

The sum equals the decimal equivalent.

Table 2. Decimal Fraction Temperature Data

0111 0011b

→ 73h → (3 × 160) + (7 × 161) = 115

Format (Local and Remote Temperature Low

Low byte conversion (for example, 0111 0000):

Bytes)

To convert the left-justified binary low-byte to

TEMPERATURE REGISTER LOW BYTE

decimal, use bits 7 through 4 and ignore bits 3

VALUE

(0.0625°C RESOLUTION)(1)

through 0 because they do not affect the value of

the number.

TEMP

STANDARD AND EXTENDED

(°C)

BINARY

HEX

0111b

→

(0

×

1/2)1

+

(1

×

1/2)2

+

0

0000 0000

00

(1 × 1/2)3 + (1 × 1/2)4 = 0.4375

0.0625

0001 0000

10

Note that the final numerical result is the sum of the

0.1250

0010 0000

20

high byte and low byte. In negative temperatures, the

0.1875

0011 0000

30

unsigned low byte adds to the negative high byte to

result in a value more than the high byte (for

0.2500

0100 0000

40

instance, –15 + 0.75 = –14.25, not –15.75).

0.3125

0101 0000

50

0.3750

0110 0000

60

0.4375

0111 0000

70

Calculation Example

0.5000

1000 0000

80

For positive temperatures (for example, +20°C):

0.5625

1001 0000

90

(+20°C)/(1°C/count) = 20

→ 14h → 0001 0100

0.6250

1010 0000

A0

Convert the number to binary code with 8-bit,

0.6875

1011 0000

B0

right-justified format, and MSB = '0' to denote a

0.7500

1100 0000

C0

positive sign.

0.8125

1101 0000

D0

+20°C is stored as 0001 0100

→ 14h.

0.8750

1110 0000

E0

For negative temperatures (for example, –20°C):

0.9375

1111 0000

F0

(|–20°C|)/(1°C/count) = 20

→ 14h → 0001 0100

(1) Resolution is 0.0625°C/count. All possible values are shown.

Generate the twos complement of a negative

number by complementing the absolute value

binary number and adding 1.

–20°C is stored as 1110 1100

→ ECh.

10

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