Codesys Sfc Example -

Transition from Step 20: Condition: (T#45s) AND NOT EStop_Pressed Supervisory Logic (Parallel Branch): IF EStop_Pressed THEN Jump to Step 99: EMERGENCY_RETRACT END_IF

Acid_Drain_Valve := FALSE; // Reset only when safe Emergency_Alerter := FALSE; Three weeks later, the line went live.

The SFC's showed:

This is how industrial programmers think. Not just "code that runs"—but . codesys sfc example

But then... nothing.

Crane_Up := TRUE; Acid_Drain_Valve := TRUE; // SD qualifier keeps this ON Emergency_Alerter := TRUE; Inside Step 0 's Entry Action:

The SFC was in with a coil halfway submerged. Transition from Step 20: Condition: (T#45s) AND NOT

The Pickle Paradox System: Industrial Pickling Line (Acid Bath for Steel Coils) Controller: CODESYS SoftPLC v3.5 SP20 Part 1: The Problem Engineer Lena Vasquez stared at the production log. Line 7, the steel coil pickling line, had just scrapped its third $40,000 coil of the week. The sequence: Load coil → Dip in HCl acid → Rinse → Dry → Unload .

"Fix it with a state machine," her manager said.

Lena needed an .

The problem was chaos. Operators would skip steps, hit "EMERGENCY RESET" mid-dip, or manually open the drain while the coil was submerged. The old ladder logic was a 40-rung monster of interlocking seals that no one understood.

She went to the Action Definition for Step 20. Instead of putting Drain_Valve := FALSE in the step's exit action, she created a Global Action called Acid_Safety and set its qualifier to SD (Set Dominant—stays TRUE until explicitly reset).

[Step 20: DIP] --(45s & no EStop)--> [Step 30: RINSE] | | (EStop_Pressed) v [Step 99: EMERGENCY_RETRACT] --(Acid_Level<5%)--> [Step 0: IDLE] Inside Step 99 's Action: But then

Lena pointed at the HMI. "No. The SFC saved it. Look—step history."