VerifAPS

PCLOpenXML support

AST and Parsing

Parser and AST for StructuredText, Sequential Function Charts and Function Blocks.

Sequential Function Chart Syntax

This is not a standard language.

Example:

SFC example

    VAR_OUTPUT
        o : bool;
    END_VAR

    STEP A
        on active action
            o := true;
        end_action
    END_STEP

    STEP B
       on active action
            o := false;
       end_action
    END_STEP

    GOTO true :: A -> B
    GOTO true :: B -> A
END_SFC

EBNF

<SFC>  :==  SFC <identifier>
                <elements>*
            END_SFC

<entry>   :== <var_decl> | <step_decl> | <transition>
<step_decl> :== STEP <identifier>
                  on <event> (action <statement>* end_action
                             | <function-identifier> )
                END_STEP
<transition> :== GOTO <guard> :: <identifier>* -> <identifier>*

<event> can be either active, exit or entry. <statement> refers to valid Structured Text statements. <var_decl> responses to classical variable declearation in IEC61131-3.