Omron NX-SL series User Manual

4 Safety Function Blocks
4 - 2
NX-series Safety Control Unit Instructions Reference Manual (Z931)
General Rules for Safety Func-
tion Blocks
This section gives the general rules for safety function blocks. Safety function block is abbreviated as
“safety FB” and “function block” is abbreviated as “FB.”
The common input variables for safety FBs are listed in the following table.
Rules That Are Specific to Safety FBs
Item Rule
Default signal The default for all SAFEBOOL signals is FALSE (i.e., the safe state).
Signal levels The values of SAFEBOOL variables have the following meanings.
• FALSE: Indicates the safe state for a system output.
• TRUE: Indicates that operation is correct in terms of system safety (e.g., that correct opera-
tion is possible).
These definitions reflect the functionality in an IEC 61131 standard. For example, if an error
occurs, all outputs change to FALSE as defined in the default signal rule.
Outputs All outputs are refreshed each safety task period.
Omitting I/O parameters You can omit parameters. Defaults are applied for any omitted parameters.
However, these defaults will not lead to a non-safe state for the system under any circum-
stances.
Defaults are defined for attributes (i.e., for variables or constants) and for FBs.
Start processing Outputs are initially set to the default values.
Outputs are enabled after the first FB call.
Error handling and diagno-
sis
All safety FBs have two error-related outputs: Error and DiagCode.
Safety FB Common Input Variables
Input param-
eter name
Data type Valid range Default Description
Activate BOOL TRUE or
FALSE
FALSE Enables and disables the FB.
You can input a variable or a constant.
The default is FALSE.
You can input a variable that gives the status of the
input device to evaluate for this parameter in order to
disable the FB and to prevent unrelated diagnostic
data from being output. If this parameter is FALSE, all
output variables take their default values.
Normally, input a TRUE constant to enable the FB.

Omron NX-SL series Specifications

General

Brand	Omron
Model	NX-SL series
Category	Control Unit
Language	English