> 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/selmo-standard-overview.md).

# Selmo standard overview

#### 1.2 The Selmo Standard

The Selmo Standard describes machines in a fixed structure:

```
PLANT(PLC)
└── Hardware zones (HWZ)
    └── Sequences (SEQ)
        └── Zones (Input, Output, In-Out, Mem)
```

Each logical process unit (e.g., stations, robot control, conveyor, etc.) is modeled as its own SEQ – with defined states and linked signals in zones. 

Each zone contains:

* Signal name
* IO definition
* HMI text
* Behavior per state (via `bit control` defined)

### 🔧 **The Selmo Standard – Overview and core functions**

The **Selmo Standard** defines a consistent structure for **modeling, control, and diagnostics** of machines. It is modular and based on three central principles:

1. **Model instead of program code**
2. **State-based behavior instead of signal sequences**
3. **Automated diagnostics through fixed system behavior**

Each machine is represented in a clear **hierarchy** :

```
Plant → Hardware Zone → Sequence → Zone
```

***

#### 🔹 **Structural elements of the Selmo Standard**

| Level             | Description                                                                                       |
| ----------------- | ------------------------------------------------------------------------------------------------- |
| **Plant**         | The entire machine or system in one PLC                                                           |
| **Hardware Zone** | A controllable machine part (e.g., station with multiple SEQs, areas) with its own operating mode |
| **Sequence**      | A logical process flow with defined states in a station (e.g., clamping, drilling)                |
| **Zone**          | A technical functional unit (e.g., cylinder, pushbutton, sensor)                                  |

***

#### 🧩 **Core functions of the Selmo Standard**

Below are the most important integrated functions that every Sequence and Zone supports according to the Selmo Standard:

***

**⚙️ 1. Bit Control (System Layer)**

* Defines per state, **how each zone behaves**
* Operands:
  * `0` = **Don’t care** – no relevance
  * `I` = **Interlock** – condition must be fulfilled
  * `S` = **Sequence Check** – action is expected and monitored
  * `M` = Monitoring - like interlock, but without shutdown - documents deviation
* Basis for automatic enable, state transitions, and error diagnostics

***

**🔍 2. Sequence Check**

* Expected action in automatic mode
* Is compared with the actual signal
* In case of deviation: **Diagnosis with blue hint in the HMI as info for the continuation condition per signal**
* Leads to the **release of the next state**, when all S are fulfilled

***

**🛑 3. Interlock Check**

* Monitors critical conditions in every state
* If an `I` is violated: **Automatic mode stops immediately**, **red error message**
* Also visible in manual mode → targeted correction possible
* Monitoring is the same function, but does not shut down

***

**🚨 4. CMZ (Constantly Monitoring Zone)**

* Permanent monitoring of safety-relevant signals
* Faults have **cross-cutting effects** on:
  * **Sequence (SEQ errors only)**
  * **Hardware Zone (all SEQ errors in the HWZ)**
  * **Plant (all HWZ errors)**
* Leads to immediate blocking of automatic mode **and** Manual mode
* Errors are **not overrideable**

***

**✋ 5. MXIC (Manual Cross Interlock Check)**

* Controls in manual mode **whether a manual movement is permitted**
* If not permitted:\
  → **no movement**,\
  → **diagnosis with explanation**, why not
* Safety logic: no manual movement against logical conditions

***

**👁️ 6. HMI linking (automatic)**

* Each zone is **HMI text** linked
* Errors are **automatically localized and color-coded**:
  * **Red** = Interlock error (No automatic mode)
  * **Blue** = Sequence Check active (Automatic possible or active in automatic)
* Operator can always see **what is expected and what is missing**

***

**⏱️ 7. Steptime**

* Time monitoring for certain states possible
* Used e.g. for waiting times, safety sequences, etc.

***

**🔁 8. Sequence Cross**

* Synchronous transitions between multiple sequences
* Enables synchronization e.g. with robot or additional stations
* Modular structure across sequence boundaries

***

**🧠 9. Parameter Layer**

* Enables definition and use of **non-binary values**:
  * Times
  * Speeds
  * Number of repetitions
* Parameters can be written directly from the HMI
* Flexibilization of the process sequence with parameters (positions, lengths, etc.)

***

**📋 10. Automatic diagnostics**

* Errors, warnings, and states are **derived from the model**
* No manual programming of diagnostics necessary
* Errors are **contextual, localized and visually recognizable, bit-precise information**

***

#### ✅ **What the Selmo Standard delivers**

| Benefit             | Description                                              |
| ------------------- | -------------------------------------------------------- |
| **Structure**       | Uniform, reusable control architecture                   |
| **safety**          | Interlocks, CMZ and MXIC as integrated safety mechanisms |
| **Transparency**    | Automatic diagnostics with clear HMI feedback            |
| **Modularity**      | Machines can be divided into and combined from sequences |
| **Maintainability** | Every process is transparently modeled, not programmed   |
| **Determinism**     | Behavior is clearly defined in every state               |


---

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