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

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.
Data name
Single-precision real number data (single-precision
floating-point data)
Double-precision real number data (double-precision
floating-point data)
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.
Sign
The following figure shows the bit configuration of the internal expression of single-precision real number data and the
meaning of each part.
b31 b30 ∙∙∙
Sign Exponent
■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
■Exponent (8 bits)
An exponent means N of 1.XXXXX2
relationships between the exponent value and N of a single-precision real number.
Exponent (b24 to b30)
N
1 OVERVIEW
48
1.2 Data Specification Method
Positive
number
Zero
Negative
number
Positive
number
Zero
Negative
number
1.
Mantissa
b23 b22 ∙∙∙ b16
N
representing a single-precision real number in binary.
N
representing a single-precision real number in binary. The following table shows the
FFH FEH FDH
Not used 127 126
Data size
32 bits (2 word)
64 bits (4 word)
Exponent
× 2
b15 ∙∙∙
Mantissa

81H 80H

2 1
Value range
-126 126
 real number<2
2
0
128 -126
-2 <real number-2
-1022 1024
 real number<2
2
0
1024 -1022
-2 <real number-2
b0

7FH 7EH 02H

0 -1 -125
01H 00H
-126 Not used