Datasheet

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
16
0
= 1 and the second number by 16
1
= 16.
0.0625 ° C, and cannot be adjusted.
The sum equals the decimal equivalent.
Table 2. Decimal Fraction Temperature Data
0111 0011b → 73h → (3 × 16
0
) + (7 × 16
1
) = 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.
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