Omron CJ - REFERENCE MANUAL 02-2010 Reference Manual page 504

3. Instructions
Floating-point Arithmetic Results
(1) Rounding Results
The following methods will be used to round results when the number of digits in the accurate result of
floating-point arithmetic exceeds the significant digits of internal processing expressions.
If the result is close to one of two internal floating-point expressions, the closer expression will be used.
If the result is midway between two internal floating-point expressions, the result will be rounded so that
the last digit of the mantissa is 0.
(2) Overflows, Underflows, and Illegal Calculations
Overflows will be output as either positive or negative infinity, depending on the sign of the result.
Underflows will be output as either positive or negative zero, depending on the sign of the result.
Illegal calculations will result in NaN. Illegal calculations include adding infinity to a number with the
opposite sign, subtracting infinity from a number with the opposite sign, multiplying zero and infinity,
dividing zero by zero, or dividing infinity by infinity.
The value of the result may not be correct if an overflow occurs when converting a floating-point number
to an integer.
(3) Precautions in Handling Special Values
The following precautions apply to handling zero, infinity, and NaN.
• The sum of positive zero and negative zero is positive zero.
• The difference between zeros of the same sign is positive zero.
• If any operand is a NaN, the results will be a NaN.
• Positive zero and negative zero are treated as equivalent in comparisons.
• Comparison or equivalency tests on one or more NaN will always be true for < > and always be false
for all other instructions.
Floating-point Calculation Results
When the absolute value of the result is greater than the maximum value that can be expressed for
floating-point data, the Overflow Flag will turn ON and the result will be output as
positive, it will be output as + ; if negative, then – .
The Equals Flag will only turn ON when both the exponent (e) and the mantissa (f) are zero after a
calculation. A calculation result will also be output as zero when the absolute value of the result is less
than the minimum value that can be expressed for floating-point data. In that case the Underflow Flag
will turn ON.
Example
In this program example, the X-axis and Y-axis coordinates (x, y) are provided by 4-digit BCD content of
D0 and D1. The distance (r) from the origin and the angle ( , in degrees) are found and output to D100
and D101. In the result, everything to the right of the decimal point is truncated.
468
P (100, 100)
y
r
0
x
CS/CJ/NSJ Series Instructions Reference Manual (W474)
. If the result is