ladder logic PLC programming instruction

The following is a growing list of ladder logic PLC programming instruction definitions and examples.

Each instruction is hyper-linked to a brief description.

The intent is to supplement the help files already provided with Studio5000 programming and configuration software. While the help files do a good job of defining the instructions, seeing believes.

The following definitions and examples are specific to Allen Bradley’s Studio 5000 software; however the concepts detailed here can be applied across multiple software applications.

Must Read : A Simple (But Complete) Guide : PLC Ladder Logic Programming(Basics)

Must Read : A Simple (But Complete) Guide: What is PLCs |PLC Basics| PLC Application|Advantage


PLC Instruction Meaning
ABS   Absolute Value
ADD   Add Instruction
AFI   Always False Instruction
AND   Bitwise And Instruction
ACS   Arc Cosine
ASN   Arc Sine
ATN   Arc Tangent
AVE   Average Instruction
BRK   Break (See FOR as well)
BSL   Bit Shift Left
BSR   Bit Shift Right
BTD   Bit Field Distribute
CLR   Clear Instruction
CMP   Compare Instruction
COP   Copy Instruction
COS   Cosine
CPS   Copy Synchronous
CPT   Compute
CTD   Count down
CTU   Count up
DEG   Radians To Degrees
DIV   Divide
EQU   Equal To
EVENT Trigger Event Task
FAL   File Arithmetic Logical
FFU   FIFO Unload
FLL   Fill File
FOR   For Routine Instruction (See BRK as well)
FRD   From BCD
FSC   File Search & Compare
GEQ   Greater Than Or Equal To
GRT   Greater Than
GSV   Get System Value
IOT   Immediate Output
JMP   Jump To Label (See LBL as well)
JSR,  SBR, RET Jump To Subroutine, Subroutine, Return From Subroutine
JXR   Jump To External Routine
LBL   Label (See JMP as well)
LEQ   Less Than Or Equal To
LES   Less Than
LFU   LIFO Unload
LIM   Limit Test
LN    Natural Log
LOG   Log Base 10
MCR   Master Control Reset
MEQ   Mask Equal
MOD   Modulo
MOV   Move
MSG   Message
MUL   Multiply
MVM   Mask Move
NEG   Negate
NEQ   Not Equal To
NOP   No Operation
NOT   Bitwise NOT
ONS   Oneshot
OR    Bitwise Inclusive OR
OSF   One Shot Falling
OSR   One Shot Rising
OTE   Output Energize
OTL   Output Latch
OTU   Output Unlatch
RAD   Degrees To Radians
RES   Reset
RET   Return From Subroutine
RTO   Retentive Timer
SBR   Subroutine
SIN   Sine
SIZE  Size array
SQI   Sequencer Input
SQL   Sequencer Load
SQO   Sequencer Output
SQR   Square Root
SRT   Sort File
SSV   Set System Value
STD   Standard Deviation
SUB   Subtract
SWPB  Swap Byte
TAN   Tangent
TND   Temporary End
TOF   Timer Off Delay
TON   Timer On Delay
TRN   Truncate
UID   User Interrupt Disable
UIE   User Interrupt Enable
XIC   Examine If Closed
XIO   Examine If Open
XOR   Bitwise Exclusive OR
XPY   X To Power Of Y