Allen-Bradley MicroLogix 1400 Instruction Manual page 232

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230 Math Instructions
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.
Data Files
Parameter
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.
Publication 1766-RM001A-EN-P - October 2008
Use the LOG instruction to take the log base 10 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 base 10 logarithm.
• Destination is the address to store the base 10 logarithm of the
Source.
Address Levels for the operands involved in the LOG 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.
Function Files
• • •
• • •
You cannot use indirect addressing with: S, MG, PD, RTC, HSC, PTOX,
IMPORTANT
PWMX, STI, EII, BHI, MMI, CS, IOS, and DLS files.
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.
(1)
Address Mode
• • •
• •
(3)
Address Level
• • •
• • •