Safe data types ensure the clear separation between safe and non-safe functionality

To avoid a possible mix-up of safe and non-safe data types (variables), the PLCopen specification defines safe data types (SAFEBOOL, etc.) which can only be used in conjunction with safety-relevant software blocks.

Corresponding plausibility checks – as they are implemented in SAFEPROG – should be performed by the programming system. To meet the programming guidelines described in the PLCopen specification, the graphical editor in the engineering software must support safety-relevant programming by means of suitable measures.

The following figure illustrates some realizations in SAFEPROG:

• Color marking of the different function block types:
  safety-FBs in dark yellow, safety functions in bright yellow, IEC 61131-FB/FU in red and user-defined FBs in green.
• Labeling of non-safe variables/data types:
  data type labels in block symbols start with 'S_', connected variables are framed with a dashed line.
• Further plausibility checks in the graphical editor...