Publication 1766-RM001A-EN-P - October 2008
Math Instructions 229
LOG - Base 10 Logarithm
Instruction Type: output
LN Instruction Operation
Inputs Conditions Output
Source Type Destination
Type
S:2/14 S:0/3-0
S, Z, V, C
S:5/0 Destination
W,DW, F F X Source > 1 0,0,0,0 L Ln(Source)
W,DW, F F X Source = 1 1,0,0,0 L 0
W,DW, F F X 0 < Source < 1 1,0,0,0 L Ln(Source)
W,DW, F W, DW X Source >= Sqrt(e) 0,0,0,0 L Rnd(Ln(Source))
W,DW, F W, DW X 1/Sqrt(e) < Source < Sqrt(e) 1,0,0,0 L 0
W,DW, F W, DW X 0 < Source <= 1/Sqrt(e) 1,0,0,0 L Rnd(Ln(Source))
(1)
+DNRM F X X 1,0,1,0 1 -INF
(1)
(2)
+DNRM W X X 1,0,1,0 1 -32768
(1)
(2)
+DNRM DW X X 1,0,1,0 1 -2147483648
(1)
(3)
W,DW, F F X Source <= 0 (including -DNRM) 0,0,1,0 1 0x7FFFFFFF
(2)
W,DW, F F X Source = +INF 0,0,1,0 1 +INF
(3)
X F X Source is NAN or -INF 0,0,1,0 1 0x7FFFFFFF
(4)
X W X Source is NAN or INF 0,0,1,0 1 32767
(4)
X DW X Source is NAN or INF 0,0,1,0 1 2147483647
(1) All denormalized inputs shall be treated as plus zero.
(2) If the Destination is word or double-word and an overflow occurs (except source is NAN or INF), destination is -32768 for Word and -2147483648 for Double Word.
(3) If the Destination is floating point, all overflows (except +INF) shall produce NAN (0x7FFFFFFF).
(4) If Destination is an integer and the Source is NAN or infinity (+INF or -INF), a saturated result (32767 for Word and 2147483647 for Double Word) shall be stored.
ABS
Log Base 10
Source N7:0
0<
Dest N7:1
0<
LOG
Execution Time for the LOG Instruction
Controller Data Size When Rung Is:
True False
MicroLogix 1400 word 112.7110 µs 0.7686 µs
long word 19.8070 µs 0.7694 µs
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