Qualifiers for Actions in SFC
You assign IEC steps to qualifiers. Qualifiers describe how an action associated with the step is executed.
The qualifiers are processed by the function block SFCActionControl
of the system library. The library is automatically integrated into the project by the SFC plug-ins.
Available qualifiers:
N | Non-stored | The action is active as long as the step is active. |
R | overriding Reset | The action is deactivated. |
S | Set (Stored) | TwinCAT executes the action as soon as the step becomes active. The action continues to be executed, even if the step has already been deactivated, until it is reset. |
L | time Limited | TwinCAT executes the action as soon as the step becomes active. The action is executed until the step becomes inactive or the specified timespan has elapsed. |
D | time Delayed | TwinCAT does not start execution of the action until the given delay time has elapsed after the step has become active and the step is still active. The action is executed until the step is deactivated. |
P | Pulse | TwinCAT executes the action precisely twice: once when the step becomes active and again in the subsequent cycle. |
SD | Stored and time Delayed | TwinCAT does not start execution of the action until the specified delay time has elapsed after the step has become active. The action is executed until it receives a reset. |
DS | Delayed and Stored | TwinCAT does not start execution of the action until the given delay time has elapsed after the step has become active and the step is still active. The action is executed until it receives a reset. |
SL | Stored and time limited | TwinCAT executes the action as soon as the step is activated. It is executed until the specified time has elapsed or a reset is received. |
You must specify the time specifications for the qualifiers L, D, SD, DS and SL in the format of a TIME constant.
When an IEC action is deactivated, it is executed one more time. This means that TwinCAT executes such an action at least twice. This also concerns actions with the qualifier P. |
See also: