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is stored in the branch on the outer right. No further timeout will be registered if a timeout occurs and
the variable SFCError is not reset again.
SFCErrorAnalyzationTable: This variable of type ARRAY [0..n] OF ExpressionResult provides the
result of an analyzation of a transition expression. For each component of the expression, which is
contributing to a FALSE of the transition and thereby to a timeout of the preceeding step, the following
information is written to the structure ExpressionResult: name, address, comment, current value.
This is possible for maximum 16 components (variables), thus the array range is max. 0..15).
The structure ExpressionResult as well as the implicitely used analyzation modules are provided with
the library AnalyzationNew.lib. The analyzation modules also can be used explicitely in other POUs,
which are not programmed in SFC.
It is a pre-condition for the analyzation of a transition expression, that a timeout is registered in the
preceeding step. So a time monitoring must be implemented there and also the variable SFCError
(see above) must be defined in the declaration window.
SFCTip, SFCTipMode: This variables of type BOOL allow inching mode of the SFC. When this is
switched on by SFCTipMode=TRUE, it is only possible to skip to the next step if SFCTip is set to
TRUE. As long as SFCTipMode is set to FALSE, it is possible to skip even over transitions.
Alternative branch
Parallel branch
Jump
Two or more branches in SFC can be defined as alternative branches. Each alternative branch must
begin and end with a transition. Alternative branches can contain parallel branches and other
alternative branches. An alternative branch begins at a horizontal line (alternative beginning) and ends
at a horizontal line (alternative end) or with a jump.
If the step which precedes the alternative beginning line is active, then the first transition of each
alternative branch is evaluated from left to right. The first transition from the left whose transition
condition has the value TRUE is opened and the following steps are activated (see active step).
Two or more branches in SFC can be defined as parallel branches. Each parallel branch must begin
and end with a step. Parallel branches can contain alternative branches or other parallel branches. A
parallel branch begins with a double line (parallel beginning) and ends with a double line (parallel end)
or with a jump. It can be provided with a jump label.
If the parallel beginning line of the previous step is active and the transition condition after this step
has the value TRUE, then the first steps of all parallel branches become active (see active step).
These branches are now processed parallel to one another. The step after the parallel end line
becomes active when all previous steps are active and the transition condition before this step
produces the value TRUE.
A jump is a connection to the step whose name is indicated under the jump symbol. Jumps are
required because it is not allowed to create connections which lead upward or cross each other.
2.2.4 Function Block Diagram (FBD)...
The Function Block Diagram is a graphically oriented programming language. It works with a list of
networks whereby each network contains a structure which represents either a logical or arithmetic
expression, the call of a function block, a jump, or a return instruction.
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