Coding Action Blocks for Steps

Action blocks are operations executed when a step is active. Steps can contain multiple action blocks of the same or different type. Add action blocks to the level 1 of a step. Depending on the action block type, program the level 2 for the block. The level 2 of an Sequential Function Chart (SFC) step is the detailed description of the actions executed during the step activity. Program level 2 code for an action block in a level 2 window, displayed to the right of the program organization unit (POU). Available action block types are:
  • Boo where the action block name is automatically associated to a Boolean variable selected from the variable selector. Possible qualifiers are Action (N), Reset (R), and Set (S).
  • LD to program an Ladder Diagram (LD) diagram in the level 2 window. Possible qualifiers are Action (N), Pulse on Deactivation Action (P0), and Pulse On Activation Action (P1).
  • SFC where the action block name is automatically associated to the SFC child. Possible qualifiers are Action (N), Reset (R), and Set (S).
  • ST to define Structured Text (ST) code in the level 2 window. Possible qualifiers are Action (N), Pulse on Deactivation Action (P0), and Pulse On Activation Action (P1).
Individual SFC steps execute in this order:
  1. Step activation - beginning when the previous transition is cleared. During this period, defined action blocks execute in the order of appearance.
  2. Step cycle - beginning when the step becomes active and ending when the step completes deactivation. During this period, defined action blocks execute in the order of appearance.
  3. Step deactivation - ending when the following transition becomes active. During this period, defined action blocks other than Boolean (Boo) action blocks with the N qualifier execute in the order of appearance. Boolean (Boo) action blocks execute after all other action blocks.
To add action blocks to steps
  1. Select the step for which to define operations.
  2. Right-click the step, point to
    Add
    , then click one of these:
    • Boo Action
    • LD Action
    • SFC Action
    • ST Action
  3. Specify the required properties for the action block from the
    Properties
     window by clicking the action block definition on the step.
    1. To rename the ST or LD action block, type the required text in the
      Name
       field.
      TIP: The names for Boo and SFC action blocks are automatically associated to their respective assignation (Boolean variable or SFC child).
    2. To specify the qualifier for the action block, select the required type in the
      Qualifier
       field.
    3. To include a comment, type the required text in the
      Comment
       field.
  4. For a Boo action block, double-click the action block name, then from the
    Variable Selector
    , select the variable for use in the block.
  5. For an ST or LD action block, access the level 2 for the block by double-clicking the action block name on the step, then program the required level 2 operations in the level 2 window displayed to the right of the POU.
  6. (optional) To rearrange the order of action blocks for a step, right-click the action block, and then click
    Move Up
     or
    Move Down
    .
  7. (optional) To delete an action block on a step, right-click the action block, and then click
    Delete
    .
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