Coordinating APL Motor Interlocks and Sequential Control Using SFC and LogicMatrix in PCS 7

To successfully coordinate an APL motor block ('MotL') with both Sequential Function Charts (SFC) and SIMATIC LogicMatrix, decouple operational state commands from safety interlocks. LogicMatrix cause-and-effect logic must be routed exclusively to the motor's interlock inputs ('Intlock', 'Permit', 'Protect'), while SFC steps write strictly to automatic control commands ('StartAut', 'StopAut'). Connecting LogicMatrix outputs directly to 'StartAut' or 'StopAut' creates continuous CFC signal conflicts that block SFC writes on every cyclic scan. Furthermore, configure 'Feature.Bit4' on MotL to define push-button or switch behavior matching your sequence design.

Executive Summary

Modern process architectures frequently combine SIMATIC LogicMatrix for cause-and-effect interlock management with SFC for procedural execution. A common integration challenge occurs when engineers attempt to wire LogicMatrix matrix outputs directly to motor operational command pins, such as StartAut or StopAut. Because CFC enforces a single continuous connection per input pin, any external CFC connection continuously overwrites step actions written by an SFC instance. This guide provides an architectural blueprint for coordinating SFC sequential execution with LogicMatrix interlock enforcement on Advanced Process Library (APL) motor blocks without signal collisions or deadlocks.

Architectural and System Mechanics

The APL MotL control model maintains a strict boundary between operational commands and interlock states:

Command Execution Path:
AutModLi & ModLiOp: Transition the motor into Automatic mode under external logic control.
StartAut / StopAut: Process commands that command the motor to start or stop when in Automatic mode.
Feature.Bit4: Selects command evaluation mode. When 0 (default), commands require a rising edge pulse; when 1, commands evaluate static levels.
Protection and Interlock Path:
Permit: Starting condition; checked only before start is initiated.
Intlock: Interlock without reset; immediately trips the running motor and prevents restart as long as active (0 = trip).
Protect: Safety interlock requiring explicit operator or program reset (RstLi).
Multi-Writer CFC Collision: Continuous CFC sheet interconnections take precedence at the start of block execution. If LogicMatrix writes to StartAut, SFC cannot alter StartAut during its step activation cycle.

Step-by-Step Engineering and Implementation Procedure

Step 1: Assign Functional Domains in CFC Architecture

Separate control logic cleanly into two domains:
1. Process Interlocks: Managed exclusively by LogicMatrix. Matrix outputs representing trips or permissives connect to Intlock or Permit.
2. State Machine Sequences: Managed exclusively by SFC. Step actions set AutModLi, StartAut, and StopAut.

Step 2: Configure MotL Operating Mode Parameters

In the CFC chart containing MotL, configure parameters to accept SFC link commands:
- Set ModLiOp = 1 to enable automatic mode selection via interconnected inputs.
- Set AutModLi = 1 in the SFC pre-start step to place the motor into Auto mode (AutAct = 1).
- Set Feature.Bit4 = 0 (pulse mode) if SFC issues momentary start pulses, or Feature.Bit4 = 1 if SFC maintains StartAut throughout the phase.

Step 3: Connect LogicMatrix Outputs to APL Interlock Inputs

Generate the CFC charts from SIMATIC LogicMatrix.
Route the LogicMatrix trip output to MotL.Intlock.
If multiple interlock sources exist (e.g., local field stop plus LogicMatrix matrix), route both into an Intlk04 block and connect its output Out to MotL.Intlock.

Step 4: Program SFC Step Actions and Transitions

In the SFC Editor:
- Step 'Start_Motor': Set MotL.StartAut = 1.
- Transition 'Motor_Running': Condition MotL.FbkRunOut.Value == 1.
- Step 'Hold_Motor': Set MotL.StartAut = 0.

Verification

To verify coordinated control:
1. In CFC test mode, confirm MotL.AutAct = 1 and MotL.Intlock.Value = 1.
2. Run the SFC chart; verify that when the start step executes, StartAut pulses and MotL.PmpRun activates.
3. Trip an input in LogicMatrix: verify that the matrix output drops to 0, MotL.Intlock drops to 0, the motor immediately trips, and the SFC holds on fault.
4. Reset the LogicMatrix condition; verify the motor remains stopped until commanded by the SFC.

Limitations and Operational Precautions

Operational precautions:
- Do not configure LogicMatrix to directly force StopAut = 1 as a safety trip; always use Intlock or Protect to ensure fail-safe de-energization.
- When using pulse mode (Feature.Bit4 = 0), ensure the SFC step execution time exceeds the AS cyclic execution period so the pulse is registered.
- Verify that emergency stop circuits bypass software logic and act directly on motor control center (MCC) power contactors.

Engineer FAQ

Q: Why does SFC fail to change `StartAut`?

A: Because an existing continuous CFC interconnection to StartAut cyclically overwrites values written by SFC.

Q: Can LogicMatrix and SFC control the same motor?

A: Yes, provided LogicMatrix connects to interlock pins (Intlock/Permit) while SFC controls operational commands (StartAut/StopAut).

Q: What does `Feature.Bit4` determine on `MotL`?

A: It sets whether automatic start and stop inputs evaluate momentary pulses (0) or sustained static levels (1).

Q: How does an interlock trip affect the SFC?

A: The motor de-energizes immediately. SFC transitions should monitor MotL.FbkRunOut or MotL.LockAct to initiate abort or holding logic.

Q: What is the difference between `Intlock` and `Protect`?

A: Intlock resets automatically when the condition clears, whereas Protect latches and requires an explicit operator reset.

Technical References

Related Tags

LogicMatrix, SFC, MotL, APL Interlocks, CFC Engineering

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Coordinating APL Motor Interlocks and Sequential Control Using SFC and LogicMatrix in PCS 7