4-2
I/O System
This section describes how the Safety CPU Unit processes I/O with external devices such as Safety
I/O Units.
When the Safety CPU Unit exchanges signals with Safety I/O Units and other external devices,
it does so through logical interfaces that are called "I/O ports".
I/O ports are created automatically when you create the control configuration for safety controls on the
Sysmac Studio and set up the safety process data communications.
You assign device variables to I/O ports to gain access to the external devices from the safety pro-
grams.
Safety CPU Unit
I/O port I/O port
Logical interface that allows the Safety CPU
Unit to exchange data with external devices
Outside of
Safety CPU
Unit
Safety I/O
Units
Safety I/O
Units
Other
Units
Variable
Device Variable
Safety programs
You can check the I/O ports in the I/O Map of the Sysmac Studio.
4-2-1
Relationship between the Types of Signals and the Types of
Communications
The safety control system uses the communications that are described below to process all I/O with
safety inputs, safety outputs, standard inputs, standard outputs, and standard controls.
•
The exchange of signals with safety inputs and safety outputs is done with safety process data com-
munications.
•
The exchange of standard signals with safety inputs, safety outputs, and standard controllers is
done with standard process data communications.
4-2-2
Safety Data Types and Standard Data Types
In this safety control system, the data type of a variable determines whether a signal is related to the
safety controls. Broadly speaking, there are the following two data types: safety data types and stand-
ard data types.
Safety Data Type Variables
A safety data type variable is a variable that specifies data that is related to safety controls.
4 Safety Control Unit Operation
4 - 8
NX-series Safety Control Unit User's Manual (Z930)
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