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MELSEC-Q/QnA
6 BASIC INSTRUCTIONS
(3) Due to the fact that floating decimal point type real numbers are processed by simple 32-bit
processing, the number of significant digits is 24 bits if the display is binary and approximately
7 digits if the display is decimal.
For this reason, if the integer exceeds the range of -16777216 to 16777215 (24-bit BIN value),
errors can be generated in the conversion value.
The conversion results round off at the 25th bit from the highest bit of the integer value, and
eliminate everything from the 26th bit and beyond.
Integer value
b23- - - - - - -b16
222030030
0 0 0 011 01001110 11 1 1 1 110 00110011 10
Becomes 222030032
Eliminated
Rounded off
After conversion
372588919
0 0 0 101 10001101 01 0 1 0 000 01011101 11
Becomes 37258891
b31- - - - - - -b24 b15- - - - - - - -b8b7- - - - - - - - b0
b23- - - - - - -b16b31- - - - - - -b24 b15- - - - - - - -b8b7- - - - - - - - b0
Eliminated
Rounded off
[Operation Errors]
(1) There are no errors associated with the FLT (P) or DFLT (P) instructions.
[Program Example]
(1) The following program converts the BIN 16-bit data at D20 to a floating decimal point type real
number and stores the result at D0 and D1.
[Ladder Mode] [List Mode]
Steps
Instruction
Device
Integer
conversion
Floating decimal point
type real number
15923
D20
BIN value
D1
15923
D0
(2) The following program converts the BIN 32-bit data at D20 and D21 to a floating decimal point
type real number, and stores the result at D0 and D1.
[Ladder Mode] [List Mode]
Steps
Instruction
Device
Integer
conversion
An error is generated in the operation result
because there are 7 significant digits
BIN value
D21
173963112
D20
BIN value
D21
16543521
D20
Floating decimal point type real number
D1
16543521
D0
D1
173963120
D0
Integer
conversion
Floating decimal point type real number
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