Basic Documentation

23 / 26
Siemens RWD Primary Controls Modbus Interface CB1P3099en_01
Building Technologies Appendix A:Standard IEEE-754 Format 27.10.2009
6 Appendix A:Standard IEEE-754
Format
According to IEEE Standard 754-1985, IEEE754 specifies binary representations for
floating point numbers.
6.1.1 General Description
A real-valued number is represented in a floating-point format as:
(-1)
Sign
× Significant ×2
Exponent
• Sign is 0 for positive values, 1 for negative values.
• Significant is a real number, composed as integer fraction, while integer=1.
• Exponent is an integer value.
6.1.2 Data Formats
The sizes of the components, in binary form, are as follows:
Exponent E Significant
Name,
Storage Size
Sign s
Width (Bias), Range Integer j Fraction f
754R Name
“Single Precision”
32 bits
1 bit:
0 → positive
1 → negative
8 bits
(127)
-126≤E≤127
1 23 bits binary32
When reading the IEEE754 format, the SEZ50MB always use “Float Inverse” for the
correct display mode for all values.
For example:
If a value is 28.6, its 32 bits binary representation is:
0100 0001 1110 0100 1100 1100 1100 1101 à 41 E4 CC CD
The byte reading sequence (in Float Inverse) of IEEE754 is 41 E4 CC CD
Note: