Macro-steps, enclosing steps and forcing

Large applications are easier to read when they are split up. GRAFCET offers three tools, all available in GrafcetMaker.

Several partial grafcets

A project can hold several partial grafcets, one per tab above the canvas, e.g. G1 for the production cycle and G2 for the safety logic. They all run at the same time and can watch each other through step variables (X21 in G1 is true while step 21 of G2 is active).

• Click + next to the tabs to add one. Its step numbers start at the next free ten (20, 30…), so Xn references stay unambiguous.
• Double-click a tab (or press F2 on it) to rename it; drag it sideways to change the order; press Del on it to delete it. Ctrl+click or Shift+click picks several tabs to delete them together. Right-click a tab for more. Many tabs scroll with the mouse wheel or the ‹ › buttons.

Macro-steps

A macro-step stands for a detailed sequence drawn on its own sheet, its expansion. It is drawn as a step with two horizontal lines.

1. Select a step and set its Kind to Macro-step in the Properties panel (or Edit › Make macro-step).
2. A new tab opens with the expansion: an entry step E and an exit step S linked by a transition. Draw the detailed sequence between them.
3. Double-click the macro-step (or press Alt+↓) to open its expansion; Alt+↑ goes back to the macro-step.

When the macro-step is activated, its entry step becomes active; the transition after the macro-step is enabled only when the exit step is active. The macro-step counts as active while any step of its expansion is.

Enclosing steps

An enclosing step contains a whole grafcet, the enclosed grafcet, that runs only while the enclosing step is active. Use it for modes: automatic, manual, setup. It is drawn as a step with two vertical lines.

1. Set the step's Kind to Enclosing step (or Edit › Make enclosing step).
2. A new tab holds the enclosed grafcet. Steps marked with * there become active when the enclosing step is activated.
3. When the enclosing step is left, every step of the enclosed grafcet is deactivated.

Tabs of expansions and enclosed grafcets carry an M or E badge.

Forcing orders

A forcing order is an action that imposes a situation on another partial grafcet while its step is active. The forced grafcet does not evolve meanwhile.

Forcing is the standard way to describe emergency stops and mode changes: a safety grafcet forces the production grafcet into its initial situation, for example. A grafcet cannot force itself, and two grafcets cannot force each other.

Checks

GrafcetMaker checks that every macro-step and enclosing step has its own sub-grafcet of the right kind, that expansions have one entry and one exit step, and that forcing orders point to existing grafcets and steps.