652
Double-precision Floating-point Instructions (CS1-H, CJ1-H, CJ1M, or CS1D Only) Section 3-16
Number of Digits Fifteen digits are effective for double-precision floating-point data.
Floating-point Data The following data can be expressed by floating-point data:
•–
∞
• –1.79769313486232 x 10
308
≤ value ≤ –2.22507385850720 x 10
–308
•0
• 2.22507385850720 x 10
–308
≤ value ≤ 1.79769313486232 x 10
30
•+∞
• Not a number (NaN)
Special Numbers The formats for NaN,
±∞, and 0 are as follows:
NaN*: e = 2,047 and f
≠ 0
+
∞: e = 2,047, f = 0, and s= 0
–
∞: e = 2,047, f = 0, and s= 1
0: e = 0 and f = 0
*NaN (not a number) is not a valid floating-point number. Executing Double-
precision Floating-point instructions will not result in NaN.
Writing Floating-point
Data
When double-precision floating-point is specified for the data format in the I/O
memory edit display in the CX-Programmer, standard decimal numbers input
in the display are automatically converted to the double-precision floating-
point format shown above (IEEE754-format) and written to I/O Memory. Data
written in the IEEE754-format is automatically converted to standard decimal
format when monitored on the display.
It is not necessary for the user to be aware of the IEEE754 data format when
reading and writing double-precision floating-point data. It is only necessary to
remember that double-precision floating point values occupy four words each.
Data No. of bits Contents
s: sign 1 0: positive; 1: negative
e: exponent 11 The exponent (e) value ranges from 0 to 2,047.
The actual exponent is the value remaining after
1,023 is subtracted from e, resulting in a range
of –1,023 to 1,024. “e=0” and “e=2,047” express
special numbers.
f: mantissa 52 The mantissa portion of binary floating-point
data fits the format 2.0 > 1.f ≥1.0.
−∞
−1
0
+∞
1
−2.22507385850720×10
-
308
−1.79769313486232×10
308
2.22507385850720×10
-
308
1.79769313486232×10
308
0
6362 5251 161532314847
f
n
se
n+3 n+2 n+1
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