SFC macro steps

A macro step is a special symbol that represents, within a SFC chart, a part of the chart that begins with a step and ends with a step. The body of the macro-step must be declared in the same program. The body of a macro-step begins with a special "begin" step with no link before, and ends with a special "end" step with no link after. The symbol of the macros step in the main chart has double horizontal lines:

A: Main Chart    B: Body of the macro-step    1: Macro step symbol    2: "Begin" step    3: "End" step

Important notes:

- The macro-step symbol and the beginning step must have the same number.
- The body of the macro-step should have no link with other parts of the main diagram (must be self-contained).
- A macro step is not a "sub program". It is just a drawing features that enables you to make clearer charts. You should never insert several macro-step symbols referring to the same macro-step body.