> For the complete documentation index, see [llms.txt](https://infosys.selmotech.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://infosys.selmotech.com/selmo-solution/selmo-solution-en/selmo-documentation-of-the-logic/sdea-model/simply-explained-sdea.md).

# Simply explained - SDEA

### 🎓 **The Selmo automaton simply explained – control, monitoring and memory**

#### 🧩 What is an automaton?

One **Automaton** is a model that describes, **how a machine thinks and reacts in states**:

* It is always in a **State**
* It **switches to the next state**, when certain conditions are met
* In each state **something happens**: A motor runs, a cylinder moves, a light turns on

This is how **every machine control works – only usually invisible**.\
Selmo makes the **visible, understandable and formally describable**.

***

### 🧠 **How does the Selmo automaton work?**

#### 1. **States**

Imagine your machine thinks in clear steps:

* "Insert part"
* "Clamp cylinder"
* "Processing running"
* "Release"
* "Remove part"

Each of these steps is a **state in the Selmo automaton**.

***

#### 2. **zones**

A **Zone** is a building block in the control – it describes e.g.:

* risk rating **Push button**
* a **valve**
* risk rating **Sensor**
* or a pure **memory bit**

Zones are linked to states – via a **table**, that precisely says:

* What should the zone do in the state?
* Should it switch something?
* Should it monitor something?
* Or is it irrelevant right now?

***

#### 3. **The Bit Control Matrix**

This table connects **zones with states** and says for each combination:

| Symbol | Meaning                                                 |
| ------ | ------------------------------------------------------- |
| `0`    | Zone is in state **irrelevant**                         |
| `S`    | Something is **expected** (e.g. that a sensor switches) |
| `I`    | Zone is **monitored** – on deviation **Error!**         |
| `M`    | Zone is monitored - on deviation documented             |

These four letters control and monitor **the entire sequence**.

***

#### 4. **What happens when a state is active?**

* **Zones with `S`** → perform something or wait for something\
  Example: Cylinder moves → sensor should report: *"I have arrived"*
* **Zones with I** → are strictly monitored, on deviation automatic stops\
  Example: A cylinder must be in position – if not: **Stop!**
* **Zone with M** → are strictly monitored, on deviation automatic stays on, but documented

As long as not everything is fulfilled, **the state waits** → the HMI indicates, **what is still missing**.

***

#### 5. **How does the machine remember something?**

With the **Mem zones**:

* A **Mem zone** is a memory: *something happened*
* Example: *"Part was inserted"* → is remembered
* Later one can react to it: *"If part is present, then..."*

The machine **remembers logically** – not by programming tricks, but **clearly modeled**.

***

#### 6. **What is special about Selmo?**

Selmo turns a machine into a **thinking, comprehensible sequence automaton**:

| Characteristic               | Explanation                                        |
| ---------------------------- | -------------------------------------------------- |
| State-based                  | Each state is defined – there is no "hidden logic" |
| Visually modeled             | You can see the sequence and every expectation     |
| Monitoring built-in          | Errors are detected automatically                  |
| Memory function              | Machine remembers what has happened                |
| Operator guidance in the HMI | Shows exactly, **what is currently expected**      |
| Safety integrated            | States stop automatically on deviation             |
| No code required             | Everything is created from the **Model**           |

***

### 📦 **What does this bring in practice?**

* **Fewer errors** during commissioning
* **Shorter development time**
* **Safe processes** in automatic and manual operation
* **Clear diagnosis** in case of malfunctions
* **Automatic documentation** of control behavior

***

### 🎯 **Summary – The Selmo automaton is:**

* One **thinking sequence**
* The **Blueprint for the machine's behavior**
* A combination of:
  * **control** (what happens)
  * **Monitoring** (what is checked)
  * **Memory** (what is remembered)

And the best part:\
**Everything is unambiguous, verifiable, documentable – all without programming tricks.**


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