B–4
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
FLOATING POINT VALUES APPENDIX B: MODBUS MAPPING FOR EPM6000
Appendix B.4 Floating Point Values
Floating Point Values are represented in the following format:
The formula to interpret a Floating Point Value is: -1
sign
x 2
exponent-127
x 1.mantissa =
0x0C4E11DB9
-1
sign
x 2
137-127
x 1
.
11000010001110111001
-1 x 2
10
x 1.75871956
-1800.929
Formula Explanation
C4E11DB9 (hex)
11000100 11100001 00011101 10111001 (binary)
The sign of the Mantissa (and therefore the number) is 1, which represents a negative
value.
The Exponent is 10001001 (binary) or 137 decimal.
The Exponent is a value in excess of 127, so the Exponent value is 10.
The Mantissa is 11000010001110110111001 binary.
With the implied leading 1, the Mantissa is (1)
.
C23B72 (hex).
The Floating Point Representation is therefore -1.75871956 x 2
10
Decimal equivalent: -1800.929
Note
Exponent = the whole number before the decimal point
Mantissa = the positive fraction after the decimal point
Register
0
1
Byte
0
1
0
1
Bit
7
6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
Meaning
s
e e e e e e e e m m m m m m m m m m m m m m m m m m m m m m m
sign
exponent
mantissa
Register
0x0C4E1
0x01DB9
Byte
0x0C4
0x0E1
0x01D
0x0B9
Bit
7
6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
1
1 0 0 0 1 0 0 1 1 1 0 0 0 0 1 0 0 0 1 1 1 0 1 1 0 1 1 1 0 0 1
Meaning
s
e e e e e e e e m m m m m m m m m m m m m m m m m m m m m m m
sign
exponent
mantissa
1
0x089 = 137
0b11000010001110110111001
