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 guide lines described in the PLCopen specification, the graphic 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 different function block types:
  Safety FBs are shown in a dark yellow, safety functions in light yellow. IEC 61131-FB/FUs are displayed in red and user-defined FBs in green.
• Clear marking 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...