Technical data

Basics of Creating Logic Blocks
10.6 Editing FBD Elements in the Code Section
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 261
Some boxes require a Boolean logic operation and some boxes must not have a Boolean logic
operation.
Boxes which require Boolean logic:
• Output, set output, reset output _/[R]
• Midline output _/[#]_/, positive edge _/[P]_/, negative edge _/[N]_/
• All counter and timer boxes
• Jump if Not _/[JMPN]
• Master Control Relay On _/[MCR<]
• Save RLO into BR Memory _/[SAVE]
• Return _/[RET]
Boxes which do not permit Boolean logic:
• Master Control Relay Activate [MCRA]
• Master Control Relay Deactivate [MCRD]
• Open Data Block [OPN]
• Master Control Relay Off [MCR>]
All other boxes can either have Boolean logic operations or not.
Enable Input/Enable Output
The enable input "EN" and enable output "ENO" of boxes can be connected but this is not
obligatory.
Removing and Overwriting
When a box is deleted, all branches which are connected to the Boolean inputs of the box are also
removed with the exception of the main branch.
The overwrite mode can be used to simply overwrite elements of the same type.
Constants
Binary links cannot be assigned constants (i.e. TRUE or FALSE). Instead, use addresses of the
data type BOOL.