Configuring Technological Actions and Commands in PCS 7 CMT and EPHT Sequences

In SIMATIC PCS 7 (V9.0 and V9.1 with SFC V9.0 SP5 Upd2), technological actions in SFC Types (such as commanding 'StartAut' on a 'MotL' block) will fail or be immediately overridden if the target input pin is directly interconnected in CFC. To execute technological actions correctly, do not hardwire the 'StartAut' pin. Instead, configure a formal 'Command' (e.g., 'SetStart') within the Control Module Type (CMT) Technological I/Os, assign the CMT to a 'Role' in the Equipment Phase Type (EPHT/EMT), and invoke the technological command within the SFC step action.

Executive Summary

With the modernization of SIMATIC PCS 7 engineering to Control Module Types (CMT) and Equipment Phase Types (EPHT), classical hardwired pin-to-pin connections in CFC are superseded by high-level technological commands and statuses. A frequent failure encountered by automation engineers occurs when attempting to command a technological block (e.g., pulsing StartAut on an APL MotL motor block) from an SFC step action.

Engineers often configure a technological action in an SFC step to set StartAut.Value := TRUE during processing and FALSE on termination, yet during testing, the drive never starts or the command fails to apply. This occurs because the engineer created a graphical interconnection between the EPH and the StartAut pin in the CFC chart. Under the PCS 7 technological model, direct chart interconnections conflict with command interfaces, locking the input. This guide details the architectural mechanics of CMT Commands and provides step-by-step instructions to implement clean, reliable technological actions.

Architecture and Fundamental Mechanics

The technological engineering framework in PCS 7 operates on an abstracted command-action-status model:

The Conflict Between Commands and Interconnections: In Step 7 / CFC, an input parameter on a block (such as MotL.StartAut) can receive its value either from a cyclic graphical interconnection (a line connecting two blocks in CFC) or from an internal variable assignment. If an input pin is connected to an external block contact or chart I/O, the CFC execution engine cyclically writes the interconnected signal into that parameter on every OB scan. If an SFC step action attempts to overwrite that parameter via a technological command, the cyclical interconnection immediately overwrites the command within the same or subsequent scan cycle, neutralizing the action.
The CMT Command Architecture: In modern PCS 7 engineering, Control Module Types (CMTs) define technological interfaces independently of graphical wiring:
- Inside the CMT Technological I/O editor, the engineer creates a 'Command' (e.g., Cmd_StartMotor).
- The Command encapsulates what happens to the underlying block contacts across the step lifecycle:
- Initialization: StartAut.Value := TRUE
- Processing: StartAut.Value := TRUE
- Termination: StartAut.Value := FALSE
Role Assignments in EPHT/EMT: In the Equipment Phase Type (EPHT), the engineer declares a 'Role' (e.g., Agitator) and assigns the CMT template to it with the option 'Basic requirement' enabled. This exposes the CMT's commands to the SFC Type editor.
Technological Action Execution: Within the SFC Type step, the engineer selects 'Technological Action' and assigns the command Agitator.Cmd_StartMotor. When the SFC sequencer enters the step, the PCS 7 execution engine executes the command cleanly through internal message brokers without requiring any hardwired CFC lines on StartAut.

Step-by-Step Implementation Procedure

Follow these steps to configure technological actions and commands cleanly in PCS 7 V9.1:

Configure Commands Inside the Control Module Type (CMT):
- In the Master Data Library, open your motor CMT (e.g., CMT_MotL) in the CFC Editor.
- Open the 'Technological I/Os' view pane ('View > Technological I/Os').
- In the technological tree, right-click 'Commands' > select 'Insert Object' > name it Cmd_Start.
- Select Cmd_Start and inspect its properties:
- Under 'Block contacts', locate the motor block's StartAut parameter.
- Configure the command action: set StartAut.Value := TRUE during 'Processing'.
- In the 'Termination' section: configure StartAut.Value := FALSE (to ensure the start signal is cleared when the step ends).
- Create a corresponding status under 'Statuses' (e.g., Stat_Running bound to MotL.FbkRun.Value = 1).
- Save the CMT.
Remove Direct Pin Interconnections to StartAut in CFC:
- In the CFC chart, inspect the MotL block.
- Ensure the input pin StartAut is completely disconnected from any chart I/Os or external driver lines.
- (Do NOT create a graphical line between the EPH and StartAut).
Assign CMT Role to the EPHT / EMT:
- In the Master Data Library, open the Equipment Phase Type (e.g., EPHT_Dosing) in the CFC Editor.
- Open the Technological I/Os view.
- Right-click 'Roles' > select 'Insert Object' > name it Role_Pump.
- Drag CMT_MotL from the catalog and assign it to Role_Pump.
- In the role properties, ensure 'Basic requirement' is checked.
Assign Technological Action in the SFC Type Step:
- Open the SFC Type inside EPHT_Dosing in the SFC Editor.
- Open the target step where the motor should run (e.g., Step_Dose).
- Open Object Properties and select the 'Technological Actions' tab (do not use the legacy Initialization/Processing tabs for this drive).
- Click 'Insert Action':
- Select the role: Role_Pump.
- Select the command: Cmd_Start.
- In the subsequent transition condition, select 'Technological Conditions':
- Condition: Role_Pump.Stat_Running = TRUE.
- Save and compile the SFC Type.
Synchronize Plant Types and Download:
- In SIMATIC Manager, execute 'Options > Plant Types > Synchronize...' to update all project instances.
- Compile CFC charts ('Changes only') and download to the AS controller.

Verification

In CFC Test Mode, open the motor chart alongside the SFC Type sequencer.
Trigger sequence advancement to Step_Dose: verify that Cmd_Start executes and MotL.StartAut switches to TRUE without hesitation.
Verify that the motor feedback confirms running, allowing the transition condition to evaluate TRUE.
Advance the sequence out of Step_Dose: verify that upon step termination, MotL.StartAut automatically resets to FALSE as defined by the command's termination rules.
Confirm zero compiler warnings regarding overlapping signal assignments in the compilation log.

Limitations and Operational Precautions

Ensure that the ModLiOp (Mode Link/Operator) parameter on the target MotL block is set to 1 (linked/automatic control enabled); if ModLiOp = 0, the block remains locked in manual operator mode and will ignore all StartAut commands regardless of technological configuration. Never mix direct graphical interconnections with technological commands on the same input pin. Validate all software engineering packages and licenses through an authorized Siemens distributor or the Siemens Industry Mall.

Engineer FAQ

Why did StartAut fail to reset when using direct CFC connections?

Direct graphical interconnections in CFC overwrite parameter assignments continuously on every CPU execution cycle. Technological commands can only manage pins that are free from competing graphical wiring.

What is the advantage of using CMT Commands over direct CFC wiring?

CMT Commands standardize actions, enforce automatic reset rules upon termination or abort, eliminate spaghetti wiring in CFC charts, and allow standardized role assignments across EPHTs.

Where are technological commands defined in PCS 7?

Commands are defined inside the Control Module Type (CMT) under the 'Commands' node in the Technological I/O view.

What happens to active technological commands if the SFC is aborted?

The SFC execution engine automatically executes the 'Termination' section of all active commands, ensuring actuators (such as valves and pumps) return to their safe, de-energized states.

Can a single SFC step trigger commands on multiple different CMTs?

Yes. A single step can contain multiple technological actions, simultaneously commanding valves to open, pumps to start, and heaters to energize across different assigned roles.