FFLD Function Blocks

Functions and function blocks can be used in FFLD diagrams.

• Blocks are always connected to the flow line (powered) by their first input and first output.
  • If the first input of a block is not Boolean, a special input called EN is added.
  • This means the block is not executed if the input flow is FALSE.
  • If the first output is not Boolean, a special output called OK is added.
    • The special OK output always has the same state as the first input (the flow).
• In a function block, the instance of the block must be specified and is shown on the top of the block.
  • Double-click the top of the block to select the instance.
  • Double-click elsewhere in the block to change its type.
• Boolean inputs and outputs of blocks can be directly linked to contacts and coils.
  • Block inputs and outputs can be specified using specific FFLD Data In / Data Out items.

• 
  

• Function and function blocks cannot be put in column 1 of the grid.
  This would not make sense because data inputs require a column.

• You cannot change a function block after it has been inserted.
• When a function is not connected on the right, it is ignored (removed at compiling time).
  • It is a case for functions only - not for function blocks.
  • A function is just part of an expression (same as a contact) and is intended to provide a result.
  • With FFLD, KAS accepts that the output is not connected because it accepts pending dead expressions to be removed at compiling time (same as contacts with no coil or FBs after).

• 
  

• If you want another function block, you first have to select it in the Libraries toolbox before inserting it.