TMP451
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SBOS686 –JUNE 2013
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 2. The measurement resolution for both the local and the
remote channels is 0.0625°C.
Table 2. 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
0000 0000
HEX
00
10
20
30
40
50
60
70
80
90
A0
B0
C0
D0
E0
F0
0
0.0625
0.1250
0.1875
0.2500
0.3125
0.3750
0.4375
0.5000
0.5625
0.6250
0.6875
0.7500
0.8125
0.8750
0.9385
0001 0000
0010 0000
0011 0000
0100 0000
0101 0000
0110 0000
0111 0000
1000 0000
1001 0000
1010 0000
1011 0000
1100 0000
1101 0000
1110 0000
1111 0000
(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.
From hexadecimal, multiply the first number by 160 = 1 and the second number by 161 = 16.
The sum equals the decimal equivalent.
0111 0011b → 73h → (3 × 160) + (7 × 161) = 115
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 → (0 × 1/2)1 + (1 × 1/2)2 + (1 × 1/2)3 + (1 × 1/2)4 = 0.4375
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.
Copyright © 2013, Texas Instruments Incorporated
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