Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual - Manual (Page 133)

Chapter 10
10-1
Maximizing System Performance
This chapter explains how to calculate throughput and provides methods
for optimizing remote I/O scan time in PLC-5/11, -5/20, -5/30, -5/40,
-5/40L, -5/60, -5/60L, and -5/80 processors.
If you want to read about: Go to page:
Components of throughput 10Ć1
Input and output modules delay 10Ć1
I/O backplane transfer
10Ć2
Remote I/O scan time 10Ć2
Processor time 10Ć6
Calculating throughput 10Ć6
For information on the time that it
takes the processor to execute a
specific instruction, see chapter 9.
Throughput is the time that it takes for an output to be energized after its
associated input has been energized. You need to consider the following
components when evaluating throughput:
input and output module delay
I/O backplane transfer
remote I/O scan time
processor time
All input and output modules have a “delay time”—the time that it takes
the module to transfer information to/from the I/O backplane through the
I/O module to/from the field device. Depending on the type of modules
you are using, these delay times vary; but the times must be taken into
account when calculating system throughput. Choose modules that
perform the function that you need with the lowest possible delay times.
Chapter Objectives
Components of Throughput
Input and Output
Modules Delay
System Design
Determined
Choosing
Communication
Transferring Discrete
and Block Data
Planning Your
System Programs
Selecting Interrupt
Routines
Maximizing System
Performance
Calculating Program
Timing
Assigning Addressing
Mode, Racks,
and Groups
Placing System
Hardware
Choosing Hardware