Rockwell Automation 1747-PTxx Getting Started Guide for HHT - Manual (Page 25)

Chapter 2
Control Basics
2–8
Processor Operating Cycle
The diagram below indicates the events that occur during the processor
operating cycle. This sequence is repeated many times each second.
Input Data File
address data
I:1 0001
( )
O:3.0
0
] [
I:1.0
0
]/[
I:1.0
1
Output Data File
address data
O:3 0000 0001
0
F8
0 1
The status of external input circuits is
read. The input data file is updated with
this information.
The ladder program is executed. The
input data file is evaluated, the ladder
rung is solved, and the output data file
is updated.
The output data file information is
transferred to the external output circuit,
thus energizing or de–energizing it.
Communications with the HHT and other
network devices takes place.
Processor internal housekeeping takes place.
Input Scan
Program Scan
Output Scan
Communications
Housekeeping
Event Description
Illuminated
activated