Omron SYSMAC CJ - REFERENCE MANUAL 08-2008 Reference Manual page 674

Floating-point Math Instructions
Description
Flags
Precautions
634
LOG(468) calculates the natural (base e) logarithm of the 32-bit floating-point
number in S+1 and S and places the result in R+1 and R.
log
S+1
e
R+1
The source data must be positive; if it is negative, an error will occur and the
instruction will not be executed.
If the absolute value of the result is greater than the maximum value that can
be expressed as floating-point data, the Overflow Flag will turn ON and the
result will be output as
Note The constant e is 2.718282.
The following diagram shows the relationship between the input data and
result.
Name
Error Flag ER
Equals Flag =
Overflow Flag OF
Underflow Flag UF
Negative Flag N
The source data in S+1 and S must be in IEEE754 floating-point data format.
Source (32-bit floating-point data)
S
Result (32-bit floating-point data)
R
.
R
Label
ON if the source data is not recognized as floating-point
data.
ON if the source data is negative.
ON if the source data is not a number (NaN).
OFF in all other cases.
ON if both the exponent and mantissa of the result are 0.
OFF in all other cases.
ON if the absolute value of the result is too large to be
expressed as a 32-bit floating-point value.
OFF
ON if the result is negative.
OFF in all other cases.
Section 3-15
S: Input data
R: Result
Operation