TMP422-EP

SBOS577

– SEPTEMBER 2011

www.ti.com

Both local and remote temperature data use two bytes for data storage. The high byte stores the temperature

with 1

°C resolution. The second or low byte stores the decimal fraction value of the temperature and allows a

higher measurement resolution, as shown in Table 3. The measurement resolution for the both the local and

remote channels is 0.0625

°C, and is not adjustable.

Table 3. Decimal Fraction Temperature Data Format (Local and Remote Temperature Low Bytes)

TEMPERATURE REGISTER LOW BYTE VALUE

(0.0625

°C RESOLUTION)(1)

TEMP

(

°C)

STANDARD AND EXTENDED BINARY

HEX

0

0000 0000

00

0.0625

0001 0000

10

0.1250

0010 0000

20

0.1875

0011 0000

30

0.2500

0100 0000

40

0.3125

0101 0000

50

0.3750

0110 0000

60

0.4375

0111 0000

70

0.5000

1000 0000

80

0.5625

1001 0000

90

0.6250

1010 0000

A0

0.6875

1011 0000

B0

0.7500

1100 0000

C0

0.8125

1101 0000

D0

0.8750

1110 0000

E0

0.9385

1111 0000

F0

(1) Resolution is 0.0625

°C/count. All possible values are shown.

Standard Binary to Decimal Temperature Data Calculation Example

High byte conversion (for example, 0111 0011):

Convert the right-justified binary high byte to hexadecimal.

The sum equals the decimal equivalent.

0111 0011b

Low byte conversion (for example, 0111 0000):

To convert the left-justified binary low-byte to decimal, use bits 7 through 4 and ignore bits 3 through 0

because they do not affect the value of the number.

0111b

Note that the final numerical result is the sum of the high byte and low byte. In negative temperatures, the

unsigned low byte adds to the negative high byte to result in a value less than the high byte (for instance,

–15 +

0.75 =

–14.25, not –15.75).

Standard Decimal to Binary Temperature Data Calculation Example

For positive temperatures (for example, +20

°C):

(+20

°C)/(+1°C/count) = 20 → 14h → 0001 0100

Convert the number to binary code with 8-bit, right-justified format, and MSB = '0' to denote a positive sign.

+20

°C is stored as 0001 0100 → 14h.

For negative temperatures (for example,

–20°C):

(|

–20|)/(+1°C/count) = 20 → 14h → 0001 0100

Generate the two's complement of a negative number by complementing the absolute value binary number

and adding 1.

–20°C is stored as 1110 1100 → ECh.

10

Submit Documentation Feedback

Copyright

© 2011, Texas Instruments Incorporated

Product Folder Link(s): TMP422-EP