Statement List (STL) - DCE FEL ČVUT v Praze

Floating-Point Math Instructions
8.4.4 LN Generate the Natural Logarithm of a Floating-Point Number
(32-Bit)
Format
LN
Description of instruction
Result
Example
LN (generate the natural logarithm of an IEEE-FP 32-bit floating-point number)
calculates the natural logarithm (logarithm to base e) of a floating-point number
(32-bit, IEEE-FP) in ACCU 1. The result is stored in accumulator 1. The input value
must be greater than zero. The instruction influences the CC 1, CC 0, UO, and OV
status word bits.
The contents of accumulator 2 (and also the contents of accumulator 3 and
accumulator 4 for CPUs with four ACCUs) remain unchanged.
The result in ACCU 1 is CC 1 CC 0 OV OS Note
+qNaN 1 1 1 1
+infinite 1 0 1 1 Overflow
+normalized 1 0 0 -
+denormalized 0 0 1 1 Underflow
+zero 0 0 0 -
-zero 0 0 0 -
-denormalized 0 0 1 1 Underflow
-normalized 0 1 0 -
-infinite 0 1 1 1 Overflow
-qNaN 1 1 1 1
STL Explanation
L MD10 //The value from memory double word MD10 is loaded into ACCU 1. (This
value must be in the floating-point format.)
LN //Calculate the natural logarithm of the floating-point number
(32-bit, IEEE-FP) in ACCU 1. Store the result in ACCU 1.
AN OV //Scan the OV bit in the status word for "0."
JC OK //If no error occurred during the instruction, jump to the OK jump
label.
BEU //Block end unconditional, if an error occurred during the
instruction.
OK: T MD20 //Transfer the result from ACCU 1 to memory double word MD20.
Statement List (STL) for S7-300 and S7-400 Programming
A5E00706960-01 8-13