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?

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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

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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

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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.