Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 147)

Output Override and I/O Update Instructions
Chapter 7
7Ć5
The Immediate Input instruction updates one word of the input image table
data in advance of the normal scan sequence (Figure 7.3). The image table
word represents one module group in the I/O chassis.
The Immediate Input instruction is programmed in the condition area of
the ladder diagram rung. The Immediate Input instruction can be
considered as always true; it is always executed, whether or not other rung
conditions allow logic continuity.
Program the Immediate Input instruction only when necessary. This
depends on both the response time of the specific input devices and
modules and on the position of the rungs examining these inputs in the
program. It is best to program the Immediate Input instruction just before
inputs in the modules group are examined in the program.
Figure 7.3
Immediate Input Instruction
Examine Bits in Word 112
Here in Program Returns to
Program
Scan
16 Bits
From One
Module Group
Written into
Imput Image
Table Word
Module
Group
(Input)
Immediate Input Instruction
Interrupts Program Scan
Word 112
I/O Scan
Program Scan
7.2.2
Immediate Input Instruction