> 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/5-logic-and-layers-dynamic/system-layer-bit-control.md). # System layer (Bit-Control) ## Define behavior The **system layer** connects the logical sequence with the real technology.\ It defines **not the sequence**, but the **expected behavior** of the zones in each state of a sequence. The goal of the system layer is to describe machine behavior: * explicitly * completely * deterministically * verifiably to describe. > **The system layer answers the question:**\ > **What must, may or does not matter – exactly in this state?** *** ### Basic principle of the system layer The system layer is based on three clear assumptions: * A sequence is in exactly **one state** * Each zone has in this state **a defined meaning** * This meaning is **explicitly specified** There are: * no implicit assumptions * no distributed logic * no interpretation-dependent evaluation *** ### The cross table (bit-control matrix) The system layer is represented as **cross table** displayed. * **Columns** → states of the sequence (logic layer) * **Rows** → zones (technology & meaning) * **Cells** → operands (`0`, `S`, `i`) This table describes: * the complete expected behavior * of all zones * in all states > **The cross table is the formal behavior model of the sequence.** *** ### The operands #### `0` – Don’t Care **Meaning:** * The zone is in this state **not relevant** * Nothing is expected * Nothing is checked * No reaction occurs **When useful:** * when a zone has no meaning for the state * to clearly decouple sequences * to reduce unnecessary dependencies > `0` is a deliberate statement – not a placeholder. *** #### `S` – Sequence Check **Meaning:** * In this state **a behavior is expected** * The system: * if necessary sets an output * waits for a defined feedback * The state is considered fulfilled when the expectation is met **Purpose:** * progress in the sequence * operator guidance * deterministic state transitions > `S` describes **Expectation**, not safety. *** #### `i` – Interlock **Meaning:** * The condition **must be fulfilled** * In case of deviation: * immediate withdrawal of automatic enable * stop the sequence * automatic diagnosis **Purpose:** * Protection of the logical sequence * Avoidance of inadmissible state combinations > `i` protects the sequence – not the machine as a whole. *** ### Meaning in automatic operation In automatic operation applies: * the sequence is driven by the system * the current state is unambiguous * the system layer is evaluated permanently Behavior of the operands: * `S` → system waits for fulfillment * `i` → system monitors mandatory condition * `0` → zone remains ignored In case of deviations: * a defined reaction occurs * is diagnosed automatically * there is no undefined state *** ### Meaning in manual operation Also in manual operation applies: * the current state remains valid * the system layer remains active * Monitoring remains fully effective The difference: * the operator influences zones manually * The goal is the **fulfillment of the state conditions** Important: * `i` continues to act as protection * `S` continues to define expectation * CMZ acts independently of the operating mode > **Manual operation is not an exception to the system layer,**\ > **but another source of influence.** *** ### Deterministic monitoring The system layer is: * evaluated continuously * applied depending on the state * monitored independently of events This means: * same conditions → same behavior * same deviation → same reaction * no situation-dependent interpretation > **Determinism arises**\ > **because behavior is fully described.** *** ### Distinction from other levels The system layer: * describes **not** * Sequence (logic layer) * Operation (hardware zone) * permanent monitoring (CMZ) * manual protective logic (MXIC) It is: * the formal connection between logic and technology * the basis for diagnosis and traceability *** ### Summary The system layer: * defines the expected behavior * makes logic explicit * prevents implicit assumptions * enables automatic diagnosis * is the basis for deterministic automation > **Without a system layer there is no verifiable machine logic.** --- # Agent Instructions This documentation is published with GitBook. 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