1766-RM001A-EN-P MicroLogix 1400 Programmable Controllers ...

228 Math InstructionsUse the LN instruction to take the natural log of the value in the sourceand store the result in the destination. The source must be greater thanzero.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, ALLdouble word, ALL float, or a combination. These operands shall undergoa conversion to float. The calculation of the source (in float) is thenperformed, and the result is then cast to the data type of Destination.LN Instruction Valid Addressing Modes and File TypesFor definitions of the terms used in this table see Using the Instruction Descriptions on page 92.Data Files Function Files (1)Address Mode (3)Address LevelParameterOISBT, C, RNFSTLMG, PDRI/RIXPLSRTCHSCPTOX, PWMXSTIEIIBHIMMILCDCS - CommsIOS - I/ODLS - Data Log (2)DirectIndirectImmediateInt16Immediate Int32Immediate FloatBitWordDouble WordElementFloatSource • • • • • • • • • • • • • •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.IMPORTANTYou cannot use indirect addressing with: S, MG, PD, RTC, HSC, PTOX,PWMX, STI, EII, BHI, MMI, CS, IOS, and DLS files.Instruction OperationWhen the rung is true, this instruction shall compute the natural logarithmof the Source and place the result in Destination.If the Destination is floating point, the result shall always be roundedusing the round to even rule.Publication 1766-RM001A-EN-P - October 2008