Transitional Instructions

Some instructions execute (or retrigger) only when rung-condition-in toggles from false to true. These are transitional-relay ladder instructions. When used in an Add-On Instruction, these instructions will not detect the rung-in transition to the false state. When the EnableIn bit is false, the Add-On Instruction logic routine no longer executes, thus the transitional instruction does not detect the transition to the false state. Extra conditional logic is required to handle triggering of transitional instructions contained in an Add-On Instruction.

Some examples of transitional instructions include: ONS, MSG, PXRQ, SRT, some of the ASCII instructions, and some of the Motion instructions.