Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 744)

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742 DMS 4.1 EN 03/2011 TD29
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13.13.7 Implicit variables - SFC flags
Each SFC step and IEC action provides implicitly generated variables for watching the
status of steps and IEC actions during runtime. Also variables can be defined for
watching and controlling the execution of a SFC (timeouts, reset, tip mode). These
variables also might be generated implicitly by the SFC object.
Basically for each step and each IEC action an implicit variable is generated. A structure
instance, named like the element, for example "step1" for a step with step name
"step1". Notice the possibility, to define in the element properties, whether for this flag
a symbol definition should be exported to the symbol configuration and how this
symbol should be accessible in the PLC.
The data types for those implicit variables are defined in library IecSFC.library. This
library will automatically be included in the project as soon as an SFC object is added.
Step and Action status and Step time
Basically for each step and each IEC-action an implicit structure variable of type
SFCStepType resp. SFCActionType is created. The structure components (flags)
describe the status of a step resp. action or the currently processed time of an active
step.
The syntax for the implicitly done variable declaration is:
: SFCStepType; resp. _ : SFCActionType;
Note: In contrast to V2.3 implicit variables for actions always are preceded by an
underscore.
The following boolean flags for step or action states are available:
For steps:
.x shows the current activation status.
._x: shows the activation status for the next cycle.
If .x = TRUE, the step will be executed in the current cycle.
If ._x = TRUE and .x = FALSE, the step will be executed in the
following cycle, that is ._x gets copied to .x at the beginning
of a cycle.
For actions:
_.x is TRUE, if the action is executed
_._x is TRUE, if the action is active