Pilz PSS SB NOT, Basic license - Manual (Page 29)

5-1 Modular Block System: Emergency Stop Circuits
Block design
Structure
Safety-related areas can be equipped with a multitude of safety devices
such as (e.g. E-STOPs, safety gates, light barriers). These safety devices
are used in various quantities and combinations, depending on the object
requiring protection.
The Modular Block System (MBS) is made up of individual standard
function blocks. A standard function block is geared towards the
requirements of specific safety devices (e.g. monitoring an E-STOP
button, safety gate monitoring).
A standard function block must be assigned to each safety device in order
for it to be evaluated and monitored using the MBS. This procedure
enables any combination of individual safety devices to be evaluated and
monitored. The standard function blocks can be combined in any
sequence within the user program (max. 600).
One exception to this are standard function blocks used to drive and
monitor contactors or valves. For control engineering reasons, these
should be called up at the end of the user program.
MBS Basics