Omron CS1G/H-CPUxxH Instructions Manual page 537

Floating-point Math Instructions
Number of Digits
Floating-point Data
Special Numbers
Writing Floating-point
Data
516
The floating-point data format conforms to the IEEE754 standards. Data is
expressed in 32 bits, as follows:
Sign Exponent
s e
31 30 23
Data No. of bits
s: sign 1
e: exponent 8
f: mantissa 23
The number of effective digits for floating-point data is 24 bits for binary
(approximately seven digits decimal).
The following data can be expressed by floating-point data:
• – ∞
38 ≤ value ≤ –1.402398 x 10
• –3.402823 x 10
• 0
≤ value ≤ 3.402823 x 10
–45
• 1.402398 x 10
• + ∞
• Not a number (NaN)
−1.402398 x 10
– ∞
38
–3.402823 x 10
The formats for NaN, ±∞ , and 0 are as follows:
NaN*: e = 255, f ≠ 0
+ ∞ :
e = 255, f = 0, s= 0
– ∞ :
e = 255, f = 0, s= 1
0: e = 0
*NaN (not a number) is not a valid floating-point number. Executing floating-
point calculation instructions will not result in NaN.
When floating-point is specified for the data format in the I/O memory edit dis-
play in the CX-Programmer, standard decimal numbers input in the display
are automatically converted to the floating-point format shown above
(IEEE754-format) and written to I/O Memory. Data written in the IEEE754-for-
mat is automatically converted to standard decimal format when monitored on
the display.
n
n+1
It isn't necessary for the user to be aware of the IEEE754 data format when
reading and writing floating-point data. It is only necessary to remember that
floating point values occupy two words each.
Mantissa
f
22
0: positive; 1: negative
The exponent (e) value ranges from 0 to 255.
The actual exponent is the value remaining after
127 is subtracted from e, resulting in a range of –
127 to 128. "e=0" and "e=255" express special
numbers.
The mantissa portion of binary floating-point
data fits the formal 2.0 > 1.f ≥1.0.
–45
38
–45
0 1
–1
15 7 6
f
s e
Section 3-15
0
Contents
–45
1.402398 x 10
38
3.402823 x 10
0
∞
+