TP1500 Comfort HMI Alarm Buffer: Configuring the Full 1024-Entry Capacity

Symptom: A Siemens SIMATIC TP1500 Comfort panel (15.4" widescreen, 1280 x 800, color TFT) is reporting only ~60 alarm events in the on-screen alarm buffer, although the panel's published performance features list a 1024-event alarm buffer. The panel appears to "wrap around" the buffer after only a few days of operation. This article walks through the root cause (alarm view filtering, not buffer exhaustion), the correct configuration steps in TIA Portal, and how to extend retention to 50,000 entries using an SD-card alarm log.

1. Problem Description

The reported symptom is consistent across several firmware generations of the TP1500 Comfort:

• The Alarm View on the TP1500 Comfort displays approximately 50-60 historical events before new events overwrite the oldest.
• The events visible in the view are only a single class (typically "Errors" or "Warnings"), not all configured classes.
• System events such as "Connection to PLC failure" or "Operator station change" do not appear in the view.
• After roughly 3 days of operation at a low event rate (~20 events/day), the buffer appears to roll over, even though no single class has reached 1024 entries.

The user expectation, set by the performance features table, is that 1024 alarm events should be retained in the volatile buffer across all configured alarm classes plus the system alarms.

2. Root Cause: Alarm View Filtering vs. Device Buffer

The TP1500 Comfort (and all Comfort Panels) maintains one shared, circular, volatile buffer in runtime memory. The published size is:

Reference: Siemens TIA Portal – Performance features of Comfort Panels (v21).

Why only ~60 entries are visible, then:

1. Single-class view: The Alarm View on the screen has only one alarm class selected. If the user enabled only "Errors" and 60 error events have fired, that view will display a maximum of 60 rows before the 61st event rolls the oldest off-screen. The remaining 964 buffer slots are still occupied by Warnings, Operator Information, and System Events that the view is not displaying.
2. System alarms filtered out: By default, the Alarm View does not include the system alarm class unless explicitly enabled in the view properties.
3. Acquired/Hidden filter: A filter set to "Show only unacknowledged" or "Show only active" will reduce the visible count even though the buffer itself is full.
4. Buffer isolation per view: If multiple Alarm Views are defined and the user has used AlarmView.GetAlarmBufferCount or equivalent, a per-view count is returned. A view that only requests one class returns the entries for that class, not the total device buffer.

3. Confirming the Root Cause on the Panel

Before reconfiguring, verify the actual buffer fill on the running panel. Two reliable methods:

3.1 Read the buffer fill from the runtime

On the TP1500 Comfort, open the Alarm View properties, and add a Status bar. Enable the "Buffer fill" column. The status bar will show e.g. 312 / 1024, proving the panel is keeping 312 events in the 1024-slot buffer even when only 60 rows are visible.

3.2 Use the WinCC Comfort online diagnostics

1. Open TIA Portal, project tree, expand Devices & Networks.
2. Right-click the TP1500 Comfort and choose Online & Diagnostics.
3. Connect to the panel over PROFINET/Ethernet.
4. Open the Diagnostics folder and select Alarm buffer. The online view shows the complete history of all classes, including system events, with timestamps and state.

4. Solution A: Display the Full Buffer in a Single Alarm View

Use this when the goal is to see all classes (errors, warnings, system events) on the panel without a log file. The change is in the view configuration, not the buffer itself.

Step 1 – Open the Alarm View configuration

1. In TIA Portal, project tree, expand HMI > HMI_1 [TP1500 Comfort] > Screens.
2. Double-click the screen containing the Alarm View (e.g. Screen_1).
3. Select the Alarm View object.
4. In the Properties window, choose Properties > General > Alarm classes.

Step 2 – Activate every configured alarm class

For each alarm class defined in the project (e.g. Errors, Warnings, System, Operator Information, Diagnostic):

• Tick the checkbox "Use this alarm class".
• Confirm the corresponding bit in the alarm class mask is set; this is the binary mask that controls which classes feed the view.

Step 3 – Add columns for full context

Under Properties > Columns, enable the following columns so each event is unambiguous:

• Number
• Time of occurrence (date and time, ms resolution)
• Alarm state (raised / cleared / acknowledged)
• Alarm class (icon + text)
• Alarm text (the multilingual text from the alarm configuration)
• Point of error (PLC tag or tag name)
• PLC / connection name

Step 4 – Configure the buffer handling for the view

1. Properties > General > Display: set "Allow operator to change buffer display" = enabled (lets the operator toggle the source buffer at runtime).
2. Properties > General > Buffer: set "Alarm buffer source" = Alarm buffer (volatile) to read the 1024-slot RAM buffer.
3. Properties > Display filter > Alarm classes: tick all classes, including System alarms and Operator information.

Step 5 – Save, compile, and download

1. Save the project (Ctrl+S).
2. Right-click the HMI device > Compile > Software (rebuild all).
3. Transfer the compiled RT to the TP1500 Comfort via Ethernet or USB.
4. Restart the panel and verify that the Alarm View now shows events from every class up to a combined 1024-slot history.

5. Solution B: Persistent Alarm Log on SD Card (50,000 entries)

The 1024-slot RAM buffer is volatile. To retain alarm history across power cycles, configure a CSV alarm log on the SD card slot (X51) on the back of the TP1500 Comfort. Each alarm class can have its own log file with up to 50,000 entries per log; the SD card's available space is the practical upper limit when multiple logs are used.

Prerequisites

Step-by-step: Create the alarm log

1. Project tree > HMI_1 [TP1500 Comfort] > Historical data > Logs.
2. Double-click Add new log. A new Log_1 is created.
3. Rename to AlarmLog_Errors (or per your naming convention).
4. In the log properties, set the Storage location to SD card (path Storage Card SD\Logs\).
5. Under Columns, add the alarm fields you want stored: Number, Time, State, Class, Text, Acknowledgement, PLC, Tag.
6. Under Properties > General > Entries, set Maximum number of entries = 50000. Set Behavior when full = Overwrite oldest entries (circular log).
7. Under Properties > Alarms, click Add. From the alarm class list, choose the classes to log: Errors, Warnings, System, Operator Information. Each class can be routed to its own log file or shared with others.

Step-by-step: Display the log on the panel

1. Project tree > Historical data > Logs > AlarmLog_Errors.
2. Open the screen that should display the historical alarm history.
3. Drag a new Alarm View onto the screen and set its Source property to Alarm log (CSV file) and select AlarmLog_Errors.
4. Set the Display filter to show all classes, all states (raised, cleared, acknowledged).
5. Compile and download.

Verifying the log is being written

1. Insert the SD card into a PC using a card reader.
2. Open \Storage Card SD\Logs\AlarmLog_Errors\.
3. A CSV file [name]_[date].csv should be present, updated in near real time. Each row is one alarm event with the configured columns.

6. Solution C: Selecting a Specific Logged View for the 250-Alarm Requirement

The original request was to display "at least 250 alarms in alarm buffer". This is achievable without a log because the device buffer is 1024 slots:

1. Open the Alarm View properties (see Section 4).
2. Set the Filter so the view receives events from all configured classes.
3. Set Sort to Time of occurrence, descending.
4. Set Scrollable = true so the operator can scroll through the entire buffer.
5. Compile and download. The view will hold the most recent 1024 events from every class combined. 250 events is well below that limit.

If the project has fewer than 250 events configured across all classes, the view will display every event; the buffer will not "wrap" until 1024 events have been generated.

7. Maximum Number of Alarms in the Buffer – Quick Reference

8. Configuration Workflow Summary

1. Step 1 – Define tags and trigger bits in the PLC (S7-1200/S7-1500). Discrete alarm: a Boolean tag, e.g. "Conveyor1.Overload". Analog alarm: a tag with configured limits.
2. Step 2 – Configure alarms in the HMI. In the HMI project, under HMI tags, mark the tag as a trigger tag and select the discrete/analog alarm type. Map it to a class (Errors, Warnings, etc.) and assign a multilingual alarm text. Reference: Configuring alarms – Basic Panels, Panels, Comfort Panels (TIA Portal v20).
3. Step 3 – Create the Alarm View on the HMI screen. Insert an Alarm View, enable all alarm classes in Properties > General > Alarm classes, and configure columns for timestamp, state, and PLC tag.
4. Step 4 – Optionally add a persistent log. Create a CSV log, set storage location to SD card, set entries to 50000, and route all alarm classes to it. Add a second Alarm View to read from the log.
5. Step 5 – Compile and download. Use Compile > Software (rebuild all) on the HMI device, then transfer the RT to the panel.

9. Troubleshooting Matrix

10. Field-Proven Caveats

• Circular behavior is normal. A circular buffer is by design: when full, the oldest entry is overwritten. This is not a bug. The 60-event behavior the user observed is a single-class view reaching the visible row count; the 1024-slot buffer itself was not full.
• System alarms count against the 1024 limit. If the user has many "Connection lost" / "Restored" events, those consume buffer slots that would otherwise be available for user alarms. Filter system alarms out of the user-facing view, but keep them in the SD-card log for diagnostics.
• RT reload clears the buffer. Each time the runtime project is reloaded on the panel, the volatile buffer is reset to zero. Plan for this when commissioning; trigger a known set of test alarms after a fresh download to verify the buffer is wired correctly.
• Time stamps use panel time. If the TP1500 Comfort's local time is not synchronized with the PLC, alarm timestamps will be inconsistent. Enable time synchronization (PLC → HMI time master) in the connection properties.
• One alarm log per class is recommended. Splitting Errors, Warnings, and System alarms into separate log files simplifies post-event analysis and reduces SD card write amplification.

11. Verification Checklist After Configuration

1. Trigger one event in every configured alarm class (e.g. set a Boolean tag true in the PLC).
2. Confirm all events appear in the Alarm View within 1-2 polling cycles.
3. Open the status bar of the Alarm View and confirm the buffer fill increments.
4. Force-fill the buffer past 250 events and verify the view still shows the most recent 250 (with scrollable = true).
5. Remove the SD card, copy the log CSV, and open it in Excel to confirm the structure.
6. Cycle power on the panel; confirm that the volatile buffer is empty and the log CSV retains all events.

12. When to Escalate

Open a case with Siemens Technical Support if any of the following are observed after applying the configuration above:

• Online diagnostics > Alarm buffer shows zero entries even though the Alarm View on the panel shows active events (RT inconsistency).
• SD-card log file is not created despite the log being configured and at least one alarm class assigned to it.
• The buffer rolls over at a number other than 1024 (e.g. 256) on a TP1500 Comfort — this would indicate a panel firmware defect.
• Alarm text shows raw text tags (e.g. @RT%1s%) instead of translated strings in a multilingual project.

When escalating, capture the following for the support case:

• Exact panel order number (e.g. 6AV2 124-1QC02-0AX0) and serial number.
• Panel firmware version (visible in Control Panel > System > Device on the panel).
• TIA Portal version and installed HSP (Hardware Support Package) version.
• A backup of the project (Project > Archive).
• Export of the SD-card log file (CSV).

13. Related Configuration Topics

• Configuring the acknowledgement of alarms: Properties > General > Acknowledgement. Errors typically require acknowledgement; Warnings and Operator Information are usually informational.
• Configuring alarm logging to a network share: a Comfort Panel can also log to a network path via SMB; the SD card is preferred for resilience against network outages.
• Email/SMS notification of alarms: route critical alarm events via the panel's SMTP client to a recipient list.
• Audit trail for GMP-regulated systems: enable the "Audit" option in the alarm log to capture the user name on acknowledge/clear actions.

FAQ