Major Design Factors Affecting Scan Time; Where To Find Scan Time Information - GE 90-30 PLC Series Installation And Hardware Manual

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Major Design Factors Affecting Scan Time

Where to Find Scan Time Information

For information on calculating scan time, please refer to the "Sweep Time Calculation" section of
GFK-0467, Series 90-30/20/Micro PLC CPU Instruction Set Reference Manual.
12-16 Series 90-30 PLC Installation and Hardware Manual – August 2002
Size of ladder program
Type of CPU. Some CPUs have faster clock speeds and architecture than others.
Types of instructions used in ladder program
Number of modules
Types of modules. Some modules, such as several of the Option modules, have a much greater
impact than others such as discrete I/O modules.
Location of modules. This refers to the type of rack (CPU, Expansion, or Remote) that they
are installed in.
Connections to other devices such as an HMI, or to other systems via communications
modules or ports.
Cable types. Cable type can have a significant impact on scan time, especially when
connecting Remote racks or communicating over long distances. Propagation time of data
should be minimized to ensure proper system timing and margins. Suggested cable types for
I/O Bus Expansion and communication cables are documented in the "Cables" chapter. Any
deviation in cable types from those recommended may result in erratic or improper
system operation.
GFK-0356Q