Omron CS1G/H-CPUxxH Instructions Manual page 593

Double-precision Floating-point Instructions (CS1-H, CJ1-H, CJ1M, or CS1D Only)
Special Numbers
Writing Floating-point
Data
Numbers Expressed as Floating-point Values
Normalized Numbers
572
• + ∞
• Not a number (NaN)
−2.22507385850720×10 -
−∞
−1.79769313486232×10
The formats for NaN, ±∞ , and 0 are as follows:
NaN*: e = 1,024 and f ≠ 0
+ ∞ :
e = 1,024, f = 0, and s= 0
– ∞ :
e = 1,024, 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.
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 isn't 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.
The following types of floating-point numbers can be used.
Mantissa (f)
0
Not 0
Note A non-normalized number is one whose absolute value is too small to be
expressed as a normalized number. Non-normalized numbers have fewer sig-
nificant digits. If the result of calculations is a non-normalized number (includ-
ing intermediate results), the number of significant digits will be reduced.
Normalized numbers express real numbers. The sign bit will be 0 for a positive
number and 1 for a negative number.
The exponent (e) will be expressed from 1 to 2,046, and the real exponent will
be 1,023 less, i.e., –1,022 to 1,023.
The mantissa (f) will be expressed from 0 to (2
in the real mantissa, bit 2
after it.
Normalized numbers are expressed as follows:
(sign s) (exponent e)–1,023
(–1) x 2
2.22507385850720×10 -
308
−1
0
308
s e
f
63 62 5251 4847 3231
n+3 n+2 n+1
Exponent (e)
0
not all 1's (1,024)
0 Normalized number Infinity
Non-normalized
number
52
is 1 and the decimal point follows immediately
x (1 + mantissa x 2
Section 3-16
308
+∞
1
308
1.79769313486232×10
1615 0
n
Not 0 and All 1's (1,024)
NaN
52
– 1), and it is assumed that,
–52
)