WinCC Flexible 2008 Data Logging: Configuring S7-300 Tag Archives

1. Overview: Data Logging in WinCC Flexible 2008

WinCC Flexible 2008 is the Siemens engineering suite used to configure HMI panels and the PC Runtime for the SIMATIC HMI family. The software supports a structured mechanism for recording process values from a SIMATIC S7 controller, stamping each record with a system time/date, persisting it to a file system, and exposing it to operators in tabular or trend form. When the controller is an S7-300 CPU 315 (typical catalog numbers 6ES7315-2EH14-0AB0, 6ES7315-2FG14-0AB0, 6ES7315-6TH13-0AB0, and the 315-2 PN/DP variants), the HMI exchanges process data over MPI, PROFIBUS, or PROFINET, and the same tags that are displayed on the screen can simultaneously be written to a Data Log (tag log) on the panel or the PC Runtime.

The mechanism relies on three objects inside the WinCC Flexible project tree:

• Tags (External tags point at S7-300 DB/bits/I/Q/M areas; internal tags are local to the HMI).
• Data Logs (also called tag logs; binary ring files stored on the HMI's storage medium).
• Logging methods (Cyclic, Event-triggered, or Command-triggered; defined per tag).

A data record written to a log contains the timestamp, the tag value, the limit violation flag, and optional user/process information. The record is also re-interpretable by the HMI Runtime for trend, table, and archive views, and can be exported to CSV for offline analysis in Excel, MATLAB, or any historian that accepts comma-separated text.

2. Prerequisites and Licensing

Before configuring the archive, verify the following engineering and runtime prerequisites.

3. Configuring Analog Tags for S7-300 315

Data logging in WinCC Flexible operates on the HMI's tag database, so the first engineering step is to define external tags that point to the data blocks (DB) of the CPU 315 where pressure and temperature values are stored as floating point (REAL / IEEE 754 single precision).

1. Open the project in WinCC Flexible 2008 and double-click Tags in the project tree.
2. Create a new tag, e.g. Pressure_01:
   • Name: Pressure_01
   • Connection: S7300_Panel (already defined under Connections > SIMATIC S7 300/400)
   • PLC address: DB 50.DBD 0 (REAL, 4 bytes)
   • Data type: Float (32-bit IEEE 754)
   • Acquisition mode: Cyclic continuous
   • Acquisition cycle: 1 s (matches a typical pressure sample rate; change to 500 ms or 250 ms if the sensor bandwidth requires it)
   • Limit monitoring: optional, e.g. 0–10 bar (tag properties > Limits)
3. Create Temp_01 with the same parameters pointing to DB 50.DBD 4.
4. Verify the tags read correctly in the offline simulation: Project > Compiler > Start Runtime Simulation, open a screen, drag the tag onto a numeric I/O field, and confirm the value reflects the simulated S7-300 area.

For S7-300 CPUs, the connection must be parameterized in Project > Connections > SIMATIC S7 300/400 with the CPU's MPI address (default 2) or the PROFINET device IP. The CPU 315-2 PN/DP variant uses TCP port 102; PROFINET IO controllers poll at 1 ms by default, but the HMI's polling rate is independent and is governed by the acquisition cycle defined on the tag.

4. Creating a Data Log (Tag Log)

The Data Log is the file object that holds the time-stamped records. A log is essentially a binary ring file that holds a configurable number of records before it overwrites the oldest entries (a circular buffer). One log can hold many tags; the trade-off is data consistency vs. file size.

1. In the project tree, right-click Data Logs > Add new Data Log.
2. Name the log, e.g. ProcessLog_01.
3. Configure the storage path:
   • For a panel: \Storage Card\Logs\ProcessLog_01
   • For PC Runtime: C:\PlantData\ProcessLog_01 (any local or UNC path)
4. Add the columns: Date, Time, Pressure_01, Temp_01, Limit.
5. Set the record count: 100,000 records for 16-bit; up to 500,000 for 32-bit. On a panel, consider storage endurance: each write is 1 flash cycle; do not write faster than 1 s on MMC.
6. Define the storage mode: Circular buffer (overwrite oldest) is the default; Linear stops when full.

The binary ring file is not directly human-readable. To read it on a PC, use the Export function on the trend view, the table view, or call the HMI function ArchiveLog with a target format of CSV. WinCC Flexible writes a header row automatically, and decimal separators follow the regional settings of the engineering station (comma vs. period).

5. Configuring Logging Cycles and Triggers

Each tag added to a Data Log can have its own logging method. The choice determines how often the tag value is appended to the log and how the time stamp is generated.

For the analog pressure/temperature channels, set:

• Pressure_01 > Logging: Cyclic, 1 s
• Temp_01 > Logging: Cyclic, 5 s (slower physical response)

To add an event-triggered entry (e.g. log only on overpressure alarm), create an internal boolean tag Alarm_PressureHigh, mark it as trigger tag, and set the log method to On change to 1. Each edge of the trigger writes a single record with the current values of all configured columns.

6. Displaying Logged Data in Runtime Tables

Operator visibility is provided by the Trend View and the Table View HMI controls. Both are bound to a Data Log, not to individual tags.

1. Open or create a screen (e.g. Process_Overview).
2. Insert a Table View from the toolbox (Controls > Table View).
3. Configure the control > Log: select ProcessLog_01.
4. Configure the columns: Date, Time, Pressure, Temperature. Uncheck columns that the operator does not need (e.g. limit status) to keep the display readable.
5. Add toolbar buttons: First record, Previous record, Next record, Last record, Stop update, Print, Export, Reload. The Export button writes a CSV copy of the visible log to a configurable path.

The Trend View control can be used in parallel and reads the same log file; the two controls are dual projections of the same data. On a TP 177B 4" panel, the table view scrolls in pages; on the PC Runtime, the table is interactive and supports Ctrl+F search via the configuration of the table's filter column.

7. CSV File Export and Storage Paths

WinCC Flexible provides three export vectors. Each is a one-time operation invoked by the operator or by a scheduled script.

7.1 Manual export from the Table View

On the Table View toolbar, click Export. The Runtime prompts for a path. Default extension is *.csv. The file layout is:

Date,Time,Pressure_01,Temp_01,Limit
21.05.2024,08:14:32,2.451,84.12,0
21.05.2024,08:14:33,2.453,84.13,0
...

Decimal separator depends on the project's regional settings: engineering stations set to German (de-DE) emit commas, US English (en-US) emits periods. This is critical for downstream parsers: Excel will refuse to import 2,451 as a number if the file is parsed under en-US locale.

7.2 Scheduled export with a VBScript or Scheduled Task

On the PC Runtime, you can attach a VBScript to a screen event that calls the HMI function ArchiveLog("ProcessLog_01", "csv", "C:\PlantData\DailyExport"). The HMI function appends a timestamp to the filename automatically, e.g. ProcessLog_01_20240521_081432.csv.

7.3 Direct file copy on panel

On a panel, the binary log file is at \Storage Card\Logs\. Connect to the panel over Ethernet (Control Panel > Transfer > Enable), then use ProSave to read the file system. The binary file is not the same as a CSV; it must be converted on the engineering station using File > Export > Convert log file.

8. Long-Term Archiving and File Management

Long-term archiving is not the same as data logging. A data log is a short-term live buffer; a long-term archive is a controlled rollover into dated CSVs that can be moved to a historian or a network share. WinCC Flexible PC Runtime supports a built-in scheduler:

1. Open the Runtime properties of the project: Project > Runtime Settings > Archives.
2. Define a Segment rollover: every day at 00:00, the active data log is closed and renamed with the date suffix, and a new file is opened.
3. Define an Archive target: local path or UNC, e.g. \\SERVER\HMI_Archive\Line1\.
4. Activate the Delete archived files older than option to enforce a retention window. Typical values are 90 days for production, 365 days for batch-pharma, indefinite for regulated environments (GxP, 21 CFR Part 11).

The resulting file structure is a daily CSV that is directly consumable by:

• Siemens WinCC / Historian (via the Connectivity Pack)
• OSIsoft PI (via the PI Interface for OPC HDA or direct file loader)
• OSIsoft PI Vision / AVEVA dashboards
• Python pandas.read_csv for ad-hoc analysis

For 21 CFR Part 11 environments, configure Audit Trail under User Administration. Every log export, log deletion, or tag value change by an operator is recorded in a separate audit log. The FDA Part 11 guidance requires that the audit trail be tamper-evident; WinCC Flexible's audit log is a signed binary, but most production sites export the audit log daily to a write-once network share.

9. Remote Access with Sm@rtAccess

The original question evolved into remote access over the Internet. WinCC Flexible exposes the Runtime over TCP/IP using the Sm@rtAccess option (also marketed as Sm@rtService for remote maintenance, and Sm@rtServer for the HMI-side service). Sm@rtAccess is the licensing option that allows an authorized client to view and operate the HMI screens from a remote location.

9.1 Licensing

Sm@rtAccess requires two licenses on a PC Runtime:

• Sm@rtServer on the HMI side (one license per HMI station that publishes its screens).
• Sm@rtClient on the viewing side (one license per simultaneous remote viewer; pool licenses are available).

On a panel, the firmware includes a single Sm@rtClient; to act as a server, the panel must support Sm@rtServer (e.g. MP 277, MP 377, or higher). The S7-300 CPU 315 plays no role in the Sm@rtAccess path; it is purely HMI-to-HMI or HMI-to-PC.

9.2 Configuring the Runtime as a Sm@rtServer

1. Open Project > Runtime Settings > Services and enable Sm@rtServer.
2. Set the listening port (default 1024, configurable to 1025/1026 for multi-station setups).
3. Under User Administration, create the remote operator accounts and assign the required rights.
4. Activate SSL/TLS (recommended); the certificate is generated on the engineering station and exported to the HMI.
5. Configure the firewall to forward the Sm@rtServer port to the HMI's IP. The typical topology is router/DSL-modem → NAT → HMI on a DMZ, with the WinCC flexible Runtime exposed on a fixed port and protected by a VPN for production deployments.

9.3 Accessing the Runtime from a client

1. Install WinCC Viewer RT (or the Sm@rtClient add-on) on the operator's PC.
2. Open a session and enter the address in the form smarthmi://<public-ip>:<port> or use the DNS name.
3. Authenticate. The session establishes a virtual screen; the operator sees the same HMI screens as if standing in front of the panel and can navigate, log in, and view the live data tables and trends.

10. Verification and Commissioning Steps

1. Compile and download the project to the HMI. On panels, transfer is performed via Ethernet or USB; on PC Runtime, just start the Runtime.
2. Open the Process_Overview screen and verify that the trend and table view populate within the first acquisition cycle (1 s for pressure, 5 s for temperature).
3. Trigger a manual log export from the Table View. Confirm the CSV opens in Excel with the correct headers and numeric values.
4. Restart the HMI Runtime. Verify that the data log re-loads from the persistent file and continues from the last record (no gap in the timeline).
5. Disconnect the PLC for 30 s. The HMI should continue to log; the tags will show the last valid value, and the log will record it. When the PLC returns, the log resumes live values. This is the "graceful degradation" behavior of WinCC Flexible.
6. If Sm@rtAccess is enabled, run a remote client session from outside the plant network and validate: login, screen navigation, table view, and trend update.

11. Troubleshooting Matrix

11.1 Diagnostic paths on the S7-300 side

When the HMI shows no data, validate the controller with STEP 7 (or TIA Portal in a migrated project):

• Open Monitor / Modify and force DB50.DBD0. The value should appear in the HMI within one acquisition cycle.
• Check the CPU's diagnostic buffer (CPU > Diagnostic Buffer) for MPI/PROFINET communication errors.
• Verify the connection resource: the S7-300 315 has a limited number of online connections (16 for the 315-2 DP, 32 for the 315-2 PN/DP). Each WinCC Runtime consumes one connection; exceeding the limit causes the CPU to reject new requests with a Connection resources exhausted diagnostic entry.

12. Migration Path to TIA Portal

For new projects, migrate the configuration to TIA Portal V17 or later. The terminology maps directly:

Migration preserves the data; TIA Portal reads the .srt file and re-emits the configuration. The license model changes: TIA Portal uses subscription-style licensing (Comfort, Advanced, Unified) and tag-count based archive licensing (Log-on-demand).

FAQ