• This graphical language is part of the IEC 1131-3 standard.
• A simple example is given below.
• A list of common mnemonics is given below. These include both the IEC 1131-3 values, and those specific to Allen Bradley controllers.
• A list of the official IEC 1131-3 mnemonics is given below,
• Here there are three types of modifiers,
N - negates an input or output
( - nests an operation and puts it on a stack to be pulled off by )
C - forces a check for the currently evaluated results
• This language uses a stack structure, like an HP calculator. When the open brackets are used the operations are pushed on the stack, closed brackets pull them back off.
• An example of an instruction language subroutine is given below. This program will examine a BCD input on card I:000, and if it becomes higher than 100 then 2 seconds later output O:001/00 will turn on.
