ST Extensions
These statements and functions are available to control the execution of Sequential Function Chart (SFC) child programs. Use these within action blocks written in Structured Text (ST) for SFC steps.
ST Statements and Functions | |||
|---|---|---|---|
GSTART | Starts an SFC program or function block | ||
GFREEZE | Freezes an SFC program | ||
GKILL | Terminates an SFC program | ||
GSTATUS | Gets the current status of an SFC program | ||
GRST | Restarts a frozen SFC program or function
block | ||
IMPORTANT:
These functions are not part of the IEC 61131-3
standard.
Simple equivalents for the GSTART and GKILL statements are available using this syntax in an SFC step:
- child_name with the S qualifier (* equivalent to GSTART(child_name); *)
- child_name with the R qualifier (* equivalent to GKILL(child_name); *)
These fields enable accessing the status of an SFC step or child (from its parent):
ST Fields | |
|---|---|
StepName.x | Boolean value that represents the activity of the Step |
StepName.t | time elapsed since the last activation of the step: activity duration (" StepName " represents the name of the SFC step) |
ChildName.__S1.x | Boolean value that represents the activity of the child |
ChildName.__S1.t | time elapsed since the last activation of the step: activity duration (" ChildName " represents the name of the SFC child) |
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