Immediate elements are located on the Utils> Immediate menu. They are supported by Snap-in I/O modules.
Generally, I/Os values are read and written to according to the PLC program scan.
Immediate elements immediately update the current value of I/Os--without regard to the program scan. This enables you:
Write values to inputs, and use the new input value to execute the rest of the PLC program.
Turn outputs ON, as for example in an emergency routine.
If your program requires you to immediately update an I/O value, use Immediate elements in conjunction with Interrupt routines.