Step

The Step represents a major function of your process. It contains the events that occur during a particular time, phase, or station.

Available Languages

Ladder Diagram

Not Available

Function Block

Not Available

Sequential Function Chart

Structured Text

Not Available

Operands

Sequential Function Chart

Operand	Type	Format	Description
Step	SFC_STEP	tag	a major function of your process containing events done during a particular time, phase, or station.

Description

The simplest way to connect steps is in sequence.

Each step uses a backing tag that provides information about the step. The following information is available via either the Step Properties dialog box or the Tags window.

If you want to	Then Check or set this member	Data type	Details
determine how long a step has been active (milliseconds)	T	DINT	When a step becomes active, the Timer (T) value resets and then starts to count up in milliseconds. The timer continues to count up until the step goes inactive, regardless of the Preset (PRE) value.
flag when the step has been active for a specific length of time (milliseconds)	PRE	DINT	Enter the time in the Preset (PRE) member. When the Timer (T) reaches the Preset value, the Done (DN) bit turns on and stays on until the step becomes active again.
	DN	BOOL	When the Timer (T) reaches the Preset (PRE) value, the Done (DN) bit turns on and stays on until the step becomes active again.
flag if a step did not execute long enough	LimitLow	DINT	Enter the time in the LimitLow member (milliseconds). If the step goes inactive before the Timer (T) reaches the LimitLow value, the AlarmLow bit turns on. The bit stays on until you reset it. To use this alarm function, turn on (check) the AlarmEnable (AlarmEn) bit.
	AlarmEn	BOOL	To use the alarm bits, turn on (check) the AlarmEnable (AlarmEn) bit.
	AlarmLow	BOOL	If the step goes inactive before the Timer (T) reaches the LimitLow value, the AlarmLow bit turns on. The bit stays on until you reset it. To use this alarm function, turn on (check) the AlarmEnable (AlarmEn) bit.
flag if a step is executing too long	LimitHigh	DINT	Enter the time in the LimitHigh member (milliseconds). If the Timer (T) reaches the LimitHigh value, the AlarmHigh bit turns on. The bit stays on until you reset it. To use this alarm function, turn on (check) the AlarmEnable (AlarmEn) bit.
	AlarmEn	BOOL	To use the alarm bits, turn on (check) the AlarmEnable (AlarmEn) bit.
	AlarmHigh	BOOL	If the Timer (T) reaches the LimitHigh value, the AlarmHigh bit turns on. The bit stays on until you reset it. To use this alarm function, turn on (check) the AlarmEnable (AlarmEn) bit.
do something while the step becomes active	X	BOOL	Use this bit for a step that does not have any actions. Typically, we recommend that you use an action with a N Non-Stored qualifier to accomplish this.
do something one time when the step becomes active	FS	BOOL	Use this bit for a step that does not have any actions. Or use this bit when all the logic for the step is called by or embedded in a single action. Typically, we recommend that you use an action with a P1 Pulse (Rising Edge) qualifier to accomplish this.
do something while the step is active, except on the first and last scan	SA	BOOL	Use this bit for a step that does not have any actions. Or use this bit when all the logic for the step is called by or embedded in a single action.
do something one time on the last scan of the step	LS	BOOL	Use this bit for a step that does not have any actions. Or use this bit when all the logic for the step is called by or embedded in a single action. Use this bit only if you do the following: On the Controller Properties dialog box, SFC Execution tab, set the Last Scan of Active Step to Programmatic reset. Typically, we recommend that you use an action with a P0 Pulse (Falling Edge) qualifier to accomplish this.
determine to which step an SFC Reset (SFR) instruction has set the SFC	Reset	BOOL	The Reset bit marks the step that will execute when an SFC Pause (SFP) instruction resumes the execution of the SFC. When an SFC Reset (SFR) instruction executes, it pauses the SFC chart and sets the Reset bit of a step in the SFC. To resume the execution of the SFC, execute an SFC Pause (SFP) instruction. This instruction starts the SFC at the step with the Reset bit on and then clears the Reset bit.
determine the maximum time that a step has been active during any of its executions	TMax	DINT	Use this for diagnostic purposes.
determine if the Timer (T) value has exceeded it upper limit	OV	BOOL	Use this for diagnostic purposes.
determine how many times a step has become active	Count	DINT	This is not a count of scans of the step. The count increments each time the step becomes active. It increments again only after the step goes inactive and then active again.
use one tag for the various status bits of this step	Status	DINT	For This Member:	Use This Bit:
			Reset	22
			AlarmHigh	23
			AlarmLow	24
			AlarmEn	25
			OV	26
			DN	27
			LS	28
			SA	29
			FS	30
			X	31

SFC Instructions

Provide Feedback

Have questions or feedback about this documentation? Please submit your feedback here.