Identifying PCS 7 Auto-Generated Tags and Implementing Standard APL Status Monitoring

In SIMATIC PCS 7, auto-generated tags in WinCC Explorer are strictly organized as Structure Tags under the 'SIMATIC S7 Protocol Suite > Named Connections' communication channel, adhering to the Plant Hierarchy naming convention [Area/Unit/]ChartName/BlockName.Parameter. Control engineers should never create loose internal tags or manually link raw peripheral addresses to animate operator buttons and equipment symbols in WinCC. Instead, standard Advanced Process Library (APL) monitoring and operator blocks must be deployed in CFC: use MonDiL (FB1848) for digital inputs, MonAnL (FB1845) for analog inputs, and OpDi01 (FB1865) or OpAnL (FB1864) for operator button controls. These blocks automatically generate standardized WinCC tags, faceplates, alarm logging events, and audit trails during OS compilation.

Architecture of PCS 7 Structure Tags in WinCC Explorer

In SIMATIC PCS 7, the Engineering Station automatically populates the WinCC Operator Station database during the OS Compilation process. Understanding how these tags appear in WinCC Explorer is essential for differentiating system-managed DCS tags from custom user additions.

When the OS Compiler scans the CFC charts:
1. It identifies all function blocks possessing the attribute s7_m_c = 'true'.
2. It generates a Structure Type in WinCC Tag Management matching the block type (e.g., MonDiL, MotL, PIDConL).
3. Under the S7 Named Connection channel, it creates a Structure Tag instance named according to the Plant Hierarchy:
$$\text{Tag Name} = \text{Area/Unit/ChartName/BlockName}$$
Individual block parameters become structure tag elements accessed using the # or . delimiter:
- Plant1/UnitA/TIC101/MonAnL.PV_Out#Value: Real process value
- Plant1/UnitA/TIC101/MonAnL.PV_Out#ST: Signal status byte (Quality Code)
- Plant1/UnitA/TIC101/MonAnL.EventState: 32-bit alarm and warning bitmask

Auto-generated tags are permanently flagged as System Tags / PCS 7 Managed. Any manual deletion or renaming of these tags inside WinCC Explorer will be immediately undone or flagged as an error during the next OS compile.

Why Manual Tag Creation Contradicts PCS 7 DCS Principles

Beginner engineers transitioning from SCADA or basic PLC environments (such as WinCC flexible or WinCC SCADA) often attempt to manually create internal binary tags or raw I/O tags in WinCC Tag Management to animate graphics (e.g., changing button colors when an input turns ON or showing a pump icon when an output turns ON).

In SIMATIC PCS 7, this practice creates severe operational and lifecycle defects:
- Destruction of Signal Quality Codes: Manual tags do not propagate the IEC 61131-3 Quality Code (ST = 16#80 for Good, 16#00 for Bad). If a field wire breaks, an HMI graphic animated via a loose tag may remain green, presenting dangerous misinformation to operators.
- Loss of Operator Authorization and Auditing: Manually drawn buttons lack integration with SIMATIC Logon, electronical signatures, and WinCC Operation Logging.
- Double Maintenance Burden: Manual tags must be mapped by hand, whereas PCS 7 automatically synchronizes thousands of tags with zero manual data entry.

Deploying Standard APL Monitoring Blocks (MonDiL, MonAnL)

To monitor field inputs and display their status on the OS:

Digital Inputs (MonDiL - FB1848)

In CFC, insert the digital input channel driver Pcs7DiIn (FB1871) connected to the physical hardware address (I 0.0).
Insert MonDiL (Monitoring Digital Large) into the chart.
Connect Pcs7DiIn.PV_Out to MonDiL.In.
Configure MonDiL properties: assign message classes and event texts in the block properties.
In WinCC, the OS Compiler automatically generates the block icon. When In transitions to TRUE, the block icon reflects the active state, logs operational messages, and updates group displays.

Analog Inputs (MonAnL - FB1845)

Insert analog channel driver Pcs7AnIn (FB1869) connected to physical address (IW 512).
Insert MonAnL (Monitoring Analog Large).
Connect Pcs7AnIn.PV_Out to MonAnL.PV.
Define high/low alarm limits (PV_AH_Lim, PV_AL_Lim).
WinCC generates standard analog faceplates, trend curves, and bar graphs with zero manual tag scripting.

Deploying Standard APL Operator Blocks (OpDi01, OpAnL)

When an operator must toggle a digital command (e.g., Start/Stop, Enable/Disable) or enter an analog setpoint from an HMI button:

Digital Operator Control (OpDi01 - FB1865)

In CFC, insert OpDi01 (Operator Dialog Digital 1).
Connect OpDi01.Out to the control logic input (e.g., a motor enable or interlock bypass) or route through Pcs7DiOu to a physical output relay.
During OS compile, WinCC instantiates the OpDi01 block icon.
When clicked in runtime, OpDi01 opens a standardized APL faceplate equipped with:
- Configurable button labels (e.g., 'Start Pump' / 'Stop Pump' via block attributes).
- Operator authorization checking (requires Operator Level 5 or 6).
- Audit trail logging in WinCC Alarm Logging capturing operator name, timestamp, and previous/new states.

Analog Operator Control (OpAnL - FB1864)

Deploy OpAnL to accept operator setpoints. The block provides high/low limit clamping (SP_OpScale) and smooth ramp rate controls before passing values to downstream PID controllers.

APL Monitoring and Operator Block Selection Matrix

The following matrix outlines the standardized APL blocks used for process visualization and operator interaction:

APL Block TypeFB NumberPrimary Operational FunctionTypical CFC InterconnectionGenerated WinCC OS ArtifactsMonDiLFB1848Digital status monitoring, alarm generation, maintenance bypassInput from Pcs7DiIn.PV_OutDigital block icon, faceplate, alarm loggingMonAnLFB1845Analog value monitoring, 4-stage limit supervision, gradient alertsInput from Pcs7AnIn.PV_OutAnalog bar graph icon, trend curves, limit alarmsOpDi01FB18651-out-of-2 operator digital selection (On/Off, Run/Stop)Output to control logic or Pcs7DiOuPushbutton faceplate with SIMATIC Logon securityOpDi03FB18661-out-of-3 operator digital selection (Manual/Auto/Cascade)Output to multi-mode selectors3-state radio button faceplateOpAnLFB1864Analog setpoint entry with rate clamping and validationOutput to PIDConL.SP_Ext or scalingSetpoint slider faceplate, high/low limits

Verification

To confirm that APL blocks are correctly integrated and visible in WinCC:
1. Compile the CFC chart containing MonDiL and OpDi01.
2. Run an OS Compile with 'Changes only'.
3. Open WinCC Explorer > Tag Management: Locate the S7 Named Connection.
4. Verify that a Structure Tag exists matching your Plant Hierarchy path (e.g., Plant1/UnitA/Pump1_Run/MonDiL).
5. Open the process picture in Graphics Designer: Verify that block icons for MonDiL and OpDi01 were automatically inserted.
6. Launch WinCC Runtime: Click the OpDi01 icon; confirm that the standard operator faceplate opens, prompts for operator confirmation, and toggles the CFC output cleanly.

Limitations and Operational Precautions

Observe the following engineering constraints:
- Do Not Modify Auto-Generated Tag Properties in WinCC: Altering structure tag data types or addresses in WinCC Explorer breaks the synchronization with the AS. Always modify block parameters in CFC.
- Process Object Licensing (PO): Every instance of MonDiL, MonAnL, or OpDi01 possessing the s7_m_c = 'true' attribute consumes 1 Process Object (PO) license in both the AS and OS. Optimize block selection to prevent unnecessary PO consumption.
- Faceplate Customization: If custom button graphics or text labels are required, configure the block parameters OS_Text1 and OS_Text2 in CFC rather than editing WinCC system scripts.

Engineer FAQ

How do I tell if a tag in WinCC was created by PCS 7 or manually by an engineer?

In WinCC Explorer Tag Management, PCS 7 tags are organized under the 'Named Connections' driver as Structure Tags with names matching the Plant Hierarchy (slashes separating folder, chart, and block names). Manually created tags typically reside under 'Internal Tags' or standard MPI/TCP channels as flat variables.

Why does my button color change fail when using manual tags?

Manual tags lack Quality Code bytes (ST). If communication is lost, manual tags retain their last state in WinCC memory, causing the button to display false status. APL blocks evaluate .PV_Out#ST and display a connection fault icon immediately upon communication loss.

Can I customize the button labels on OpDi01?

Yes. In the CFC chart, select OpDi01 and open Object Properties. In the 'Text 0' and 'Text 1' fields (or parameters OS_Text1 / OS_Text2), enter your custom text (e.g., 'Purge Active' / 'Purge Idle'). The faceplate updates automatically upon OS compile.