Troubleshooting Equipment Phase (EPH) and Equipment Module (EM) Command Handshakes in PCS 7

When an Equipment Phase (EPH) in SIMATIC PCS 7 runs its sequence but fails to start or command its associated Equipment Module (EM / EMT) in runtime, the primary cause is an operating mode mismatch: the SFC of the Equipment Module must be in Automatic mode (AutAct = 1) to accept supervisory commands (e.g., START, COMPLETE, ABORT) from the parent EPH. If the EM is in Manual mode, it intentionally rejects automatic commands. To resolve this: (1) Switch the EM SFC to Automatic mode; (2) Verify that the EPH command successfully allocates and acquires the EM without conflict from competing phases; and (3) If block contacts appear unresponsive, remove the EM assignment from the EPH in the instance, refresh with F5, re-assign the EM, and compile the OS.

Executive Summary

In modular automation and recipe-controlled facilities engineered under ISA-88 standards with SIMATIC PCS 7, Equipment Phase Types (EPHT / EPH) coordinate procedural control by commanding lower-level Equipment Module Types (EMT / EM) and Control Modules (CMT). Commissioning engineers frequently encounter an execution deadlock where both the EPH and the EM run perfectly when tested independently in manual mode, but when the EPH sequence executes and commands the EM to start, the associated EM remains completely idle. Furthermore, because PCS 7 manages EPH-to-EM signaling via hidden technological block contacts rather than visible CFC wires, engineers struggle to diagnose why commands fail. This article explains the automatic command handshake and allocation rules governing modular Equipment Phases.

Architecture and Fundamental Mechanics

The procedural handshake between Equipment Phases and Equipment Modules operates through technological state machines:

Operating Mode Governance (Automatic vs. Manual):
- An Equipment Module (EM) is governed by an underlying Sequential Function Chart (SFC) or SFC Type representing its physical state machine.
- In Manual Mode, the EM responds exclusively to operator commands from the WinCC faceplate. It strictly ignores external procedural commands to prevent unexpected mechanical motion during local testing.
- In Automatic Mode (ModLiOp = 1, AutAct = 1), the EM transfers command authority to the supervisory level, allowing an active EPH to issue commands such as START, PAUSE, RESUME, COMPLETE, and ABORT.
The Allocation and Acquisition Mechanism:
- Before an EPH can command an EM, it must successfully Acquire (allocate) the equipment. This prevents two concurrent phases (e.g., Dosing Phase A and Dosing Phase B) from driving the same physical dosing pump simultaneously.
- In the EPH step action, the command AcquireEM requests ownership. The EM verifies that it is currently unowned (Owner == 0) and not in a faulted state, then assigns its ownership token to the requesting EPH (Owner == EPH_ID). If acquisition fails, subsequent StartEM commands are discarded.
Technological Block Contacts (No Visible CFC Wires):
- In Control Module Technology (CMT/EMT), communication between EPH and EM does not use manual CFC lines. Instead, PCS 7 utilizes Block Contacts generated automatically by the Plant Hierarchy and Technological Editor.
- The EPH references the EM by its technological name. If the technological link is broken during chart renaming or partial copying, the underlying block contacts desynchronize, preventing runtime command transmission.

Step-by-Step Implementation Procedure

Diagnose and resolve EPH-to-EM command communication using the following procedure:

Verify EM Operating Mode Online:
- Open the WinCC OS faceplate or online SFC chart for the target Equipment Module (EM).
- Inspect the operating mode. If it displays Manual, switch it to Automatic.
- In CFC, ensure that ModLiOp = 1 and AutData = 1 so that supervisory logic retains automatic command control.
Verify Allocation and Ownership Status:
- Open the online view of the EPH chart.
- In the step actions preceding the start command, verify that the acquisition instruction is executed: e.g., EM_Dosing.Acquire := 1.
- Inspect the EM block pins: confirm that Allocated = 1 and CurrentOwner matches the technological ID of the EPH.
- If the EM is locked by another phase or an unreleased batch, execute a reset or release command (ReleaseEM := 1).
Refresh Technological Block Contacts:
- In SIMATIC Manager Plant View, locate the hierarchy folder containing the EPH instance.
- Open the Technological Editor (View -> Technological Views).
- Under the EPH technological I/Os, locate the Equipment Module assignment.
- If the link appears broken, delete the EM reference, press F5 to refresh the database, and drag the target EM instance back into the assignment field.
- Right-click the AS project and select Plant Types -> Synchronize.
Recompile OS and Download Changes:
- Compile CFC charts (Changes Only).
- Compile the WinCC OS to update server data and faceplate cross-references.
- Download changes to the AS controller in RUN mode.

Verification

Verify automated procedural execution:

Automatic Handshake Test: Place the EM into Automatic mode. Initiate the EPH sequence from the WinCC faceplate or SIMATIC BATCH.
Dynamic Step Monitoring: Observe the EPH step progression. Confirm that upon reaching the command step, the EM's SFC transitions instantly from Ready to Starting and enters Running.
Completion and Release Verification: Allow the EM to finish its technological task. Confirm that the EM signals Completed back to the EPH, allowing the EPH transition to advance, and that the EM ownership token is cleanly released.

Limitations and Operational Precautions

Never attempt to draw manual CFC signal wires between internal EPH and EM blocks to bypass block contacts; doing so violates CMT/EMT abstraction boundaries, causes compiler errors during bulk synchronization, and breaks SIMATIC BATCH recipe coordination. Always rely on technological assignments and ensure automatic operating modes.

Engineer FAQ

Why must the EM be in Automatic mode for the EPH to command it?

In Manual mode, the EM is under exclusive manual operator control. To prevent unexpected automated equipment operation, the EM rejects all external start and step commands unless placed into Automatic mode.

Why are there no visible CFC interconnections between EPH and EM?

CMT and EMT architectures utilize technological 'Block Contacts' managed by the PCS 7 database, eliminating cluttered inter-chart wires and enabling modular type synchronization.

What happens if two EPH instances try to acquire the same EM simultaneously?

The EM grants ownership to the first requesting phase. The second phase's acquisition request is held pending until the first phase executes a release command.

Can an EM command lower-level Control Modules (CMs)?

Yes. An Equipment Module (EM) encapsulates and commands multiple lower-level Control Modules (e.g., pumps, valves, transmitters) using the same technological block contact principles.

What is the difference between an EPH and an EMT?

An EMT (Equipment Module Type) defines equipment logic and subordinate devices. An EPHT/EPH (Equipment Phase Type) defines the procedural recipe phase that coordinates one or more EMTs.