Step Types
The following types of steps exist:
Type |
Representation |
Description |
|---|---|---|
"Normal" Step |
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A step becomes active when the previous step becomes inactive (a delay that may be defined must pass) and the upstream transition is satisfied. A step normally becomes inactive when a delay that may be defined passes and the downstream transition is satisfied. For a parallel joint, all previous steps must satisfy these conditions. Zero or more actions belong to every step. Steps without action are known as waiting steps. |
Initial step |
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The initial status of a sequence string is characterized by the initial step. After initializing the project or initializing the sequence string, the initial step is active. Initial steps are not normally assigned with any actions. With Single-Token (Conforming with IEC 61131-3) only one initial step is allowed per sequence. With Multi-Token, a definable number (0 to 100) of initial steps are possible. |
Macro Step |
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See Macro Step |
Input step |
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see Input Step |
Output step |
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see Output Step |
Step Names
When creating
a step, it is assigned with a suggested number. The suggested number
is structured as follows S_i_j, whereas i is the (internal) current number of the section and j is the (internal) current step number in the current section.
You can change the suggested numbers to give you a better overview. Step names (maximum 32 characters) must be unique over the entire project, i.e. no other step, variable or section etc. may exist with the same name. There are no case distinctions. The step name must correspond with the standardized name conventions.
Step Times
Each step can be assigned a minimum supervision time, a maximum supervision time and a delay time:
Minimum Supervision Time
The minimum supervision time sets the minimum time for which the step should normally be active. If the step becomes inactive before this time has elapsed, an error message is generated. In animation mode, the error is additionally identified by a colored outline (yellow) around the step object.
If no minimum supervision time or a minimum supervision time of 0 is entered, step supervision is not carried out.
The error status remains the same until the step becomes active again.
Maximum Supervision Time
The maximum supervision time specifies the maximum time in which the step should normally be active. If the step is still active after this time has elapsed, an error message is generated. In animation mode, the error is additionally identified by a colored outline (pink) around the step object.
If no maximum supervision time or a maximum supervision time of 0 is entered, step supervision is not carried out.
The error status remains the same until the step becomes inactive.
Delay Time
The delay time (step dwell time) sets the minimum time for which the step must be active.
Setting the Step Times
The following formula is to be used for defining/determining these times:
Delay time< minimum supervision time< maximum
supervision time
There are 2 ways to assign the defined values to a step:
As a duration literal
Use of the data structure
SFCSTEP_TIMES
SFCSTEP_TIMES Variable
Every step can be implicitly
allocated a variable of data type SFCSTEP_TIMES.
The elements for this data structure can be read from and written
to (read/write).
The data structure is handled the same as any other data structure, i.e. they can be used in variable declarations and therefore accessing the entire data structure (e.g. as FFB parameter) is possible.
Structure of the Data Structure:
Element Name |
Data type |
Description |
|---|---|---|
|
|
Delay Time |
|
|
Minimum Supervision Time |
|
|
Maximum Supervision Time |
SFCSTEP_STATE Variable
Every step is implicitly allocated
a variable of data type SFCSTEP_STATE. This step
variable has the name of the allocated step. The elements for this
data structure can only be read (read only).
You can see the SFCSTEP_STATE variables in the . The for a SFCSTEP_STATE variable is the
comment entered as a property of the step itself. Please refer to
chapter Defining the properties
of steps.
The data structure cannot be used in variable declarations. Therefore, accessing the entire data structure (e.g. as FFB parameter) is not possible.
Structure of the Data Structure:
Element Name |
Data type |
Description |
|---|---|---|
|
|
Current dwell time in the step. If the step is deactivated, the value of this element is retained until the step is activated again. |
|
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1: Step active 0: Step inactive |
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This element is a supplement to IEC 61131-3. 1: Underflow of minimum supervision time 0: No underflow of minimum supervision time The element is automatically reset in the following cases:
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This element is a supplement to IEC 61131-3. 1: Overflow of maximum supervision time 0: No overflow of maximum supervision time The element is automatically reset in the following cases:
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