CODESYS · Track 03 · IEC 61131-3 + CFC

Six Languages, One Logic

CODESYS implements every IEC 61131-3 language — LD, FBD, ST, IL, SFC — and adds its own free-form CFC (Continuous Function Chart), where you place blocks anywhere and draw the wires yourself. Here's the same motor seal-in across the four you'll use most. The standout is CFC: signal flow with no grid.

🪜 LD🔲 FBD⌨️ ST🔗 CFC
01 · The Rosetta Stone

Start · seal-in · stop

Press Start → the motor runs and seals in; press Stop → it drops. Switch tabs — Ladder, FBD, Structured Text and CFC all show the same live logic. (IL and SFC exist too; we cover SFC-style sequencing in the Schneider & Siemens academies.)

⊣ ⊢
Start
⊣/⊢
Stop
( )
Motor
⊣ ⊢
Motor (seal-in)
Start
Motor
Stop
≥1
OR
&
AND
Motor
Motor := (Start OR Motor) AND NOT Stop;
// CODESYS ST — the IEC standard, OOP-extended (Track 04)
Start
Motor
Stop
≥1
OR
&
AND
Motor
▶ Start
⛔ Stop
Motor: OFF
⚙️

In CFC the blocks float and you route the wires by hand — no left-to-right rung rule. Engineers love it for signal flow that doesn't fit a grid (mixing, math chains, analog conditioning). Same compiled logic as the others; total freedom of layout.

02 · Check yourself

What makes CFC special?

How does CFC differ from FBD?