Mitsubishi Electric MELSEC iQ-R Series - Real Number Data (Floating-Point Data)

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1 OVERVIEW
1.2 Data Specification Method
Real number data (floating-point data)
Data size and data range
Real number data includes single-precision 32-bit real number data and double-precision 64-bit real number data.
Real number data can be stored only in devices other than bit devices or in single-precision or double-precision real data type
labels.
Configuration of single-precision real number data
Single-precision real number data consists of a sign, mantissa, and exponent, and is expressed as shown below.
The following figure shows the bit configuration of the internal expression of single-precision real number data and the
meaning of each part.
■Sign (1 bit)
This bit represents the positive or negative sign of a numerical value. "0" indicates a positive number or 0. "1" Indicates a
negative number.
■Mantissa (23 bits)
A mantissa means XXXXX of 1.XXXXX2
N
representing a single-precision real number in binary.
■Exponent (8 bits)
An exponent means N of 1.XXXXX2
N
representing a single-precision real number in binary. The following table shows the
relationships between the exponent value and N of a single-precision real number.
Data name Data size Value range
Single-precision real number data (single-precision
floating-point data)
Positive
number
32 bits (2 word) 2
-126
 real number<2
126
Zero 0
Negative
number
-2
128
<real number-2
-126
Double-precision real number data (double-precision
floating-point data)
Positive
number
64 bits (4 word) 2
-1022
 real number<2
1024
Zero 0
Negative
number
-2
1024
<real number-2
-1022
Exponent (b24 to b30) FFH FEH FDH  81H 80H 7FH 7EH  02H 01H 00H
N Not used 127 126  210-1 -125 -126 Not used
1. × 2
MantissaSign
Exponent
b31 b30
 b23 b22 b16 b15 b0
Sign Exponent Mantissa