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FX3S/FX3G/FX3GC/FX3U/FX3UC Series
Programming Manual - Basic & Applied Instruction Edition
5 How to Specify Devices and Constants to Instructions
5.1 Numeric Values Handled in PLC (Octal, Decimal, Hexadecimal and Real Numbers)
Scientific notation (real number)
Because binary floating point (real number) is difficult to understand for users, it can be converted into scientific
notation (real number). But internal operations are executed using binary floating point (real number).
Scientific notation (real number) is handled by a pair of data registers having serial device numbers. Different from
binary floating point (real number), a data register having a smaller device number handles the mantissa part, and the
other data register having a larger device number handles the exponent part.
For example, when data registers D1 and D0 are used, they handle scientific notation as shown below. Data can be
written to D0 and D1 by MOV instruction.
Scientific notation (real number) = [Mantissa D0] × 10 [Exponent D1]
Mantissa D0 = ± (1000 to 9999) or 0
Exponent D1 = −41 to +35
The most significant bit of D0 and D1 specifies the positive or negative sign respectively, and is handled as the
complement of 2 respectively.
The mantissa D0 does not allow "100", for example. In the case of "100", it is handled as "1000 × 10
−1
".
The scientific notation (real number) range is as follows:
- Minimum absolute value: 1175 × 10
−41
- Maximum absolute value: 3402 × 10
35
Number of significant figures
The number of significant figures of scientific notation is approximately 4 when expressed in decimal. The scientific
notation range is as described above.
Scientific notation (real number) is valid in the following instructions:
- Conversion from binary floating point (real number) into scientific notation (real number): FNC118 ([D]EBCD)
- Conversion from scientific notation (real number) into binary floating point (real number): FNC119 ([D]EBIN)