FX Series Programmable Controllers | Devices in Detail 4 |
4.15.1Scientific Notation
This format could be called the step between the ‘integer’ formats and the full floating point formats. In basic terms Scientific Notation use two devices to store information about a number or value. One device contains a data string of the actual characters in the number (called the mantissa), while the second device contains information about the number of decimal places used in the number (called the exponent). Hence, Scientific Notation can accommodate values greater/smaller than the normal 32 bit limits, i.e.
Maximums | Minimums |
9999 ✕ 1035 | 9999 ✕ |
Scientific Notation can be obtained by using the BCD, or EBCD in FX2N, instruction (FNC 18 or FNC 118) with the float flag M8023 set ON. In this situation floating point format numbers are converted by the BCD instruction into Scientific Notation - see page
Scientific Notation can be converted back to floating point format by using the BIN instruction (FNC 19) with the float flag M8023 set ON - see page
The following points should be remembered about the use of Scientific Notation within appropriate FX units;
• The mantissa and exponent are stored |
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in consecutive data registers. |
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Each part is made up of 16 bits and can |
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| EXPONENT |
| MANTISSA |
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be assigned a positive or negative value |
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| Data Register D+1 |
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| Data Register D |
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indicated by the value of the most |
| b15 |
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| b0 | b15 |
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| b0 |
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significant bit (MSB, or bit 15 of the data |
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register) for each number. |
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| Sign bit (MSB) | Sign bit (MSB) | |||||||||||
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| 1= Negative | 1= Negative | |||||||||||
• The mantissa is stored as the first 4 |
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| 0 = Positive | 0= Positive | |||||||||||
significant figures without any rounding |
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of the number, i.e. a floating point number of value 2.34567 ✕ 103 would be stored as a mantissa of 2345 at data register D and an exponent of 0 (zero) at data register D+1.
•The range of available mantissa values is 0, 1000 to 9999 and
•The range of available exponent values is +35 through to
•Scientific format cannot be used directly in calculations, but it does provide an ideal method of displaying the data on a monitoring interface.
