1 Overview
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NX-series Safety Control Unit User’s Manual (Z930)
The safety control system uses the communications that are described below to process all I/O with
safety inputs, safety 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 in the standard control system is done with standard process data
communications.
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 stan-
dard data types.
Safety Data Type Variables
A safety data type variable is a variable that specifies data that is related to safety controls.
The names of safety data type variables have the word SAFE appended to a standard data type
name, such as SAFEBOOL and SAFEBYTE.
Refer to 7-2-5 Data Types on page 7-15 for details on the safety data types.
Standard Data Type Variables
These variables represent data that is not related to safety controls.
Refer to 6-7 Exposing Variables to Standard Controllers on page 6-20 for details on how to access
standard data type variables from NJ/NX-series CPU Units and other standard controllers.
Each type of signal is defined with a standard data type or safety data type as shown below.
The following table shows how safety data type variables and standard data type variables are used
based on the type of communications.
• Signals that are input and output through safety process data communications must be defined as
safety data type variables.
• Signals that are input and output through standard process data communications must be defined as
standard data type variables.
Types of Signals and Relationship between the Types of Communi-
cations
Safety Data Types and Standard Data Types
Type of signal Data type of variable to use
Outputs from safety control to standard control Standard data type
Inputs from standard control to safety control
Safety inputs from external devices Safety data type
Safety outputs to external devices
Internal safety-related signals with no I/O with any external devices Safety data type
Internal standard-related signals with no I/O with any external devices Standard data type
Specifying Safety Data Types and Standard Data Types
Units
Communications type Data type of variable to use
Master Slaves
Safety CPU Unit Safety I/O Units Safety process data commu-
nications
Safety data type variables
NJ/NX-series CPU Unit
or other standard con-
troller
Safety CPU Unit Standard process data com-
munications
Standard data type variables
Safety I/O Units
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