Publication 1766-RM001A-EN-P - October 2008
228 Math Instructions
Use the LN instruction to take the natural log of the value in the source
and store the result in the destination. The source must be greater than
zero.
Enter the following parameters when programming this instruction:
• Source is the address to compute the natural log.
• Destination is the address to store the natural log of the Source.
Address Levels for the operands involved in the LN can be ALL word, ALL
double word, ALL float, or a combination. These operands shall undergo
a conversion to float. The calculation of the source (in float) is then
performed, and the result is then cast to the data type of Destination.
Instruction Operation
When the rung is true, this instruction shall compute the natural logarithm
of the Source and place the result in Destination.
If the Destination is floating point, the result shall always be rounded
using the round to even rule.
LN Instruction Valid Addressing Modes and File Types
For definitions of the terms used in this table see Using the Instruction Descriptions on page 92.
Parameter
Data Files
Function Files
(1)
CS - Comms
IOS - I/O
DLS - Data Log
(2)
Address Mode
(3)
Address Level
O
I
S
B
T, C, R
N
F
ST
L
MG, PD
RI/RIX
PLS
RTC
HSC
PTOX, PWMX
STI
EII
BHI
MMI
LCD
Direct
Indirect
Immediate
Int16
Immediate Int32
Immediate Float
Bit
Word
Double Word
Element
Float
Source •• •••• • • • • • •• •
Destination • • • • • • • •
• • •• •
(1) PTOX and PWMX files are only for use with MicroLogix 1400 BXB or BXBA unit.
(2) The Data Log Status file can only be used for the following math instructions: ADD, SUB, MUL, DIV, NEG, and SCP.
(3) See Important note about indirect addressing.
IMPORTANT
You cannot use indirect addressing with: S, MG, PD, RTC, HSC, PTOX,
PWMX, STI, EII, BHI, MMI, CS, IOS, and DLS files.
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