Application Note for “Usage of AC500 digital standard I/Os in functional safety applications up to PL c (ISO 13849-1)”, V1.0.0
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1 Introduction
1.1 Purpose
The number of used digital safety input channels in safety applications is often signifi-
cantly higher than the number of digital safety output channels. In some customer PLC
applications, there are often free spare digital standard I/O channels. There is a ques-
tion if these free spare digital standard I/O channels can be used together with SM560-
S Safety CPU to realize functional safety functions. If yes, one could avoid using addi-
tional Safety I/O modules with digital safety input channels and, thus, save control sys-
tem costs and reduce control cabinet dimensions in some customer applications.
We analyzed a possible usage of AC500 digital standard I/Os to realize functional
safety functions. This application note describes a possible usage of digital standard
I/O modules from AC500 platform (www.abb.com/PLC) in functional safety application
up to PL c (ISO 13849-1). The functional safety calculation according to ISO 13849-1
is used as an example to show the compliance of the proposed approach with the
relevant functional safety requirements for PL c (ISO 13849-1). The functional safety
calculation according to IEC 62061 standard (applications up to SIL CL 1) can be sim-
ilarly done, if required.
In special cases, digital standard I/O modules from AC500 platform can be also used
in functional safety applications up to PL d (ISO 13849-1) and SIL CL 2 (IEC 62061).
However, more detailed functional safety application analysis is required (contact
AC500 technical support at www.abb.com/PLC for more details) and, thus, is not
shown in this document.
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