SIMATIC PCS 7 Process Object (PO) Calculation and License Counting Rules

Process Objects (POs) in SIMATIC PCS 7 are technological runtime licenses and cannot be determined solely by applying fixed multipliers to field I/O counts. An AS RT PO license is consumed exclusively by technological blocks that possess operator control and monitoring capability (S7_m_c := 'true') and generate system alarms via internal messaging blocks (ALARM_8P). Technological control blocks such as MotL, VlvL, and PIDConL each consume exactly one AS RT PO, whereas raw signal driver blocks (Pcs7AnIn, Pcs7DiIn) and pure logic blocks consume zero POs. To establish exact licensing requirements, calculate technological device instances using the Process Object View and verify booked capacity in Automation License Manager.

Fundamentals of Process Object Licensing in SIMATIC PCS 7

SIMATIC PCS 7 utilizes a technological licensing model known as Process Objects (PO) to scale system capacity and enforce software licensing across automation systems (AS) and operator stations (OS). Distinguishing between different PO categories is vital for architectural accuracy:

AS Runtime Process Objects (AS RT PO): License blocks running on the controller. In traditional modular S7-400 CPUs (e.g., CPU 416-3, CPU 417-4H), AS RT POs are software license keys stored in Automation License Manager (ALM) on the Engineering Station and booked to the CPU chart container during compilation.
CPU 410-5H System Expansion Card (SEC): For the CPU 410-5H Process Automation controller, AS PO capacity is embedded directly in hardware via a physical System Expansion Card plugged into the rear of the CPU, available in capacities from 100 PO to 2000+ PO.
OS Runtime Process Objects (OS RT PO): Licenses running on WinCC OS Servers, determining the maximum number of technological objects represented across operator graphics and alarm management.

Why I/O Rules of Thumb Fail in Technological Sizing

Engineers frequently attempt to estimate PO requirements from raw I/O counts using rough rules of thumb (such as 'DI divided by 3' or 'all AI + AO + DO'). While useful as an early conceptual budgeting heuristic, relying on I/O ratios for procurement leads to severe license shortages or costly over-licensing:

Variable Signal Density: A single modulating control valve with feedback, alarms, and interlocks consumes 1 AO, 1 AI, 2 DO, and 2 DI (6 physical I/O channels) but represents exactly one AS RT PO (VlvAnL).
Zero-PO Signals: Raw analog and digital indicators utilizing driver blocks Pcs7AnIn and Pcs7DiIn consume field I/O but zero AS RT POs because they do not instantiate internal alarm generation.
Complex Logic and Multiplexing: Motor starters controlled via fieldbus (e.g., SIRIUS over PROFINET) consume zero physical I/O modules but consume one full AS RT PO for technological control.

AS RT PO Consumption Rules by Block Family

The table below details specific PCS 7 Advanced Process Library (APL) block families and their exact AS RT PO consumption rules.

Block Type / FamilyExample APL BlocksOperator Controllable (S7_m_c)Alarm Generation (ALARM_8P)AS RT PO ConsumedMotor ControlMotL, MotRevL, MotSpdCLYes (true)Yes (ALARM_8P internal)1 PO per instanceValve ControlVlvL, VlvMotL, VlvAnLYes (true)Yes (ALARM_8P internal)1 PO per instanceContinuous ControllersPIDConL, PIDConR, FmContYes (true)Yes (ALARM_8P internal)1 PO per instanceDose / Batch BlocksDoseLYes (true)Yes (ALARM_8P internal)1 PO per instanceAnalog / Digital MonitoringMonAnL, MonDiLYes (true)Yes (ALARM_8P internal)1 PO per instanceSignal Channel DriversPcs7AnIn, Pcs7AnOu, Pcs7DiInYes / NoNo (No ALARM_8P)0 POInterlock Logic BlocksIntlk02, Intlk04, Intlk08Yes (faceplate view)No (No ALARM_8P)0 POMathematical / Logic GatesAdd04, Mul04, AND, ORNoNo0 PO

Equipment Schedule and License Ordering Reference

The following equipment schedule lists official Siemens software runtime packages and hardware expansion cards used to scale Process Object capacity.

License / Package NameMLFB / Order NumberLicense TypeScope and FunctionalitySIMATIC PCS 7 AS RT PO (100 PO)6ES7658-2BA00-0YB0Software Runtime LicenseExpands modular AS runtime capacity by 100 process objectsSIMATIC PCS 7 AS RT PO (500 PO)6ES7658-2BB00-0YB0Software Runtime LicenseExpands modular AS runtime capacity by 500 process objectsSIMATIC PCS 7 OS RT PO (100 PO)6ES7658-2XA00-0YB0Software Runtime LicenseExpands WinCC OS Server runtime capacity by 100 process objectsCPU 410-5H System Expansion Card (PO 500)6ES7653-2CA00-0XB0Hardware Capacity DongleActivates 500 PO capacity directly on CPU 410-5H hardwareCPU 410-5H System Expansion Card (PO 1000)6ES7653-2CC00-0XB0Hardware Capacity DongleActivates 1000 PO capacity directly on CPU 410-5H hardware

[!IMPORTANT]
Commercial Accuracy and Procurement Disclaimer: Final licensing counts and MLFB selections must be verified against > official Siemens product documentation and quotation from an authorized distributor. Configuration tools such as CDT are > planning aids and do not guarantee final runtime licensing entitlements.

Step-by-Step Procedure to Audit Booked POs in PCS 7

Follow this procedure in SIMATIC Manager to determine exact PO consumption for an existing project:

Open Process Object View:
- In SIMATIC Manager, select View -> Process Object View (or click the Process Object View toolbar icon).
- Highlight the multiproject root or specific automation system.
Inspect Technological Blocks Tab:
- Select the General tab to see total technological block counts.
- Select the Blocks tab: filter by column PO relevant to see every block actively consuming a process object.
Audit Booked License Capacity:
- In Component View, select the target AS CPU.
- Select Options -> Charts -> Process Objects -> Display booked process objects.
- Review the dialog displaying: 'Licensed POs', 'Booked POs', and 'Available POs'.
Verify OS Server PO Licensing:
- Open WinCC Explorer on the OS Server, launch Automation License Manager, and verify that the WinCC Server RT PO license key matches or exceeds total booked OS objects.

Verification

Verify PO license integrity through the following checks:
1. In Process Object View, confirm that 'Booked POs' does not exceed the 'Licensed POs' threshold.
2. Compile CFC charts: ensure compilation finishes without license warning dialogs (e.g., 'License shortage: PO limit exceeded').
3. In Automation License Manager, verify that license keys for AS RT PO and OS RT PO show valid status without expiration dates.
4. On redundant OS servers, verify that identical OS RT PO license quantities are installed on both Server A and Server B.

Limitations and Operational Precautions

Exceeding booked AS RT PO limits in modular S7-400 systems allows compilation but triggers continuous license warning popups in SIMATIC Manager and logs compliance violations in the Windows Event Viewer. On CPU 410-5H systems, exceeding hardware System Expansion Card limits prevents CFC delta downloads entirely. Never rely on I/O estimates for ordering; always base procurement on the actual count of technological control loops (MotL, VlvL, PIDConL, MonAnL).

Engineer FAQ

Does Pcs7AnIn consume an AS Process Object?

No. Raw signal channel drivers (Pcs7AnIn, Pcs7DiIn) do not have internal ALARM_8P message blocks and do not consume an AS RT PO. If analog alarm monitoring is required, interconnecting Pcs7AnIn to MonAnL consumes 1 PO for the MonAnL block.

How are POs licensed on redundant OS Servers?

OS Runtime PO licenses must be purchased and installed in full for each redundant OS server independently. If a project requires 1000 OS POs, Server A requires a 1000 PO license and Server B requires an identical 1000 PO license.

Can unused PO licenses be returned to the ALM license pool?

Yes, for modular S7-400 software licenses (6ES7658-2...) using 'Options -> Charts -> Book back process objects'. However, hardware SEC capacity on CPU 410-5H cannot be returned to ALM once assigned to a CPU.