Implementing Chronological Messaging with S7-400 and WinCC

1. Overview

Chronological messaging (German: "Chronologische Meldeanzeige") is a Siemens HMI concept in which alarms are time-stamped at the PLC (S7-300/S7-400) and read by the HMI for display. Because the time stamp originates in the CPU rather than in the panel, the displayed sequence remains consistent even when the HMI is restarted, the project is reloaded, or the panel has been disconnected from the network.

For a CPU 412-2 PN paired with a TP1200 Comfort, chronological messaging requires:

• STEP 7 V18 or higher in the Professional edition (or STEP 7 Professional in TIA Portal V13 SP1 and newer). STEP 7 Basic cannot configure S7-300/S7-400 devices and cannot be used for this application.
• WinCC Comfort/Advanced/Professional in the same TIA Portal installation.
• CPU 412-2 PN firmware V6.0 or higher (recommended V6.0.7 or newer to cover all SFC17/18 corrections).
• TP1200 Comfort with WinCC Comfort V18 (or matching the TIA Portal version).

The reference implementation published by Siemens (entry ID 23730697) describes the configuration on the S7-400 and WinCC side. This article extends that document with the connection-setup steps that the source FAQ explicitly excludes, plus the SFC17/SFC18 call mechanics and the TP1200 message-view wiring.

2. Prerequisites

3. How Chronological Messaging Works on S7-400

Unlike a discrete alarm that is acknowledged in the HMI, a chronological message is generated and time-stamped in the CPU, transferred once to the HMI, and stored in the HMI's chronological message buffer. The HMI never re-sends the message; it only displays what the CPU has announced.

3.1 SFC17 vs. SFC18 selection

For TP1200 Comfort and the standard chronological message list, use SFC18 for non-acknowledgeable events (e.g., threshold transitions, set-point reached) and SFC17 for events that the operator must acknowledge (e.g., fault, E-Stop). The time stamp resolution is 10 ms on S7-400 CPUs; the panel displays it in the configured date/time format.

4. Project and Connection Setup

1. Open TIA Portal and create a new project. Do not use a project migrated from STEP 7 V5 - the S7-400 must be added as a device in the TIA Portal project tree.
2. Add the CPU 412-2 PN from the hardware catalog. TIA Portal places the PROFINET interface (X1) automatically.
3. Add the TP1200 Comfort to the same project and connect its PROFINET port to the CPU's PROFINET subnet. TIA Portal will create an HMI connection with the type S7-300/400.
4. Open Devices & Networks > Connections. Confirm that the connection type is S7-300/400 and the partner end is the CPU 412-2 PN. If TIA Portal proposes S7-1200, the HMI project was created with a different CPU family and must be re-linked.

The official Siemens "Communication with SIMATIC S7 300/400" chapter in the TIA Portal Help (V20 edition) covers the same connection model for Basic Panels, Panels, Comfort Panels, RT Advanced and RT Professional:

Communication with SIMATIC S7 300/400 - TIA Portal Help (V20)

4.1 Connection diagnostics

On the HMI side, open Connections > [connection name] > Properties and verify:

• Address: the HMI's IP address
• Partner address: the CPU's IP address
• Connection resource ID: 0 (default) for the first S7-300/400 partner
• Slot / Rack: 0 / 0 (rack 0, slot 2 = CPU)

5. PLC Program: Calling SFC18 (Example)

Create a function block (FB) in the S7-400 program and call SFC18 once for every event you want to log. Use an associated value to attach process state (e.g., the actual torque in Nm) to the message.

ST example (SCL)

// FB "Chrono_Alarms" - call site in OB1
"Inst_Chrono"(Trigger := bAlarmActive,
            EV_ID   := 1,
            SIG     := 1,
            SD      := REAL#42.5,         // associated value (Nm)
            RET_VAL := iSfc18Ret);

IF iSfc18Ret <> 0 THEN
    // SFC18 error - store in diagnostics DB
    "dbDiag".lastSfc18Error := iSfc18Ret;
END_IF;

LAD example - place SFC18 in a network with the following parameter mapping:

5.1 Common SFC18 RET_VAL codes

6. HMI Configuration in TIA Portal (TP1200 Comfort)

1. Open the TP1200 device in the project tree.
2. Navigate to Alarm logs > Chronological. This buffer stores all messages received via the S7-300/400 connection. Set the size (default 500 messages is sufficient for most lines).
3. Open HMI tags > Show all tags and create a tag of the same name and data type that the PLC uses for the SFC18 associated value (e.g., rTorque, REAL, length 4). Map it to the PLC tag over the S7-300/400 connection.
4. Open the screen that should display the messages. Drag the Alarm control (or Alarm view) onto the screen and configure:
   • Source: Chronological log
   • Columns: date/time, message text, state, associated value
   • Layout: classic ("WinCC Classic") for S7-300/400 connections

7. Message Text and Associated-Value Configuration

The TIA Portal WinCC editor does not define free text for chronological messages. The text is generated by the CPU when it calls SFC17/18, because the message text plus the format specification are part of the S7-400 project (STEP 7 V5 or TIA Portal). Specifically:

1. On the S7-400 device, open PLC alarms > Text lists.
2. Create one text list entry per EV_ID. Example for EV_ID 1:
   • Range start: 1
   • Range end: 1
   • Text: Motor torque reached
3. On the message view side, the alarm control will display the text from the PLC without any further mapping.

8. Commissioning Procedure

1. Compile the S7-400 project and download the hardware configuration to the CPU.
2. Download the user program (OB1, FB, DB, SFC18 calls) to the CPU.
3. Compile the TP1200 project and download it to the panel. Use Extended download to transfer the runtime image.
4. Set the IP addresses of CPU and panel on the same subnet. The CPU's IP must match the connection partner in TIA Portal.
5. Trigger one of the SFC18 events from the program (set a tag, force the input in the watch table).
6. Verify the message appears in the TP1200 alarm view with the correct time stamp.
7. Cycle power on the HMI. After restart, the chronological message buffer must still contain the previously received events.

9. Verification and Diagnostics

Use the following checks after commissioning to confirm the chronological pipeline is healthy.

9.1 Connection status on the HMI

Open the TP1200 system screen System > Connections. The S7-300/400 partner must show status Connected. If it shows Disconnected, check:

• PROFINET cabling and link LEDs
• IP address and subnet mask of both ends
• PG/PC and HMI are on the same subnet (no router between them)
• The connection resource ID on the HMI side has not been duplicated

9.2 PLC-side SFC status

Monitor the SFC18 RET_VAL in a watch table. A constant value of W#16#0000 confirms the CPU has handed the message to the PN stack. A constant W#16#8001 indicates the partner registration is missing; re-check the connection under Devices & Networks on the TIA Portal side.

9.3 Buffer verification

On the TP1200, the chronological message list is a ring buffer. When the configured size is reached, the oldest entry is overwritten. Increase the buffer size in Alarm logs > Chronological > Size if older events must be retained (max 9999 entries on Comfort V18).

10. Troubleshooting Matrix

11. Comparison: Chronological vs. Non-Chronological

12. Reference Documents

The following Siemens documents were used to validate the procedure:

• Chronological messaging with an S7-400 CPU and WinCC - Siemens Industry Online Support (ID 23730697)
• Communication between WinCC (TIA Portal) and S7-300/400 - Siemens Industry Online Support (ID 62121503)
• Communication with SIMATIC S7 300/400 - TIA Portal Help V20
• SFC18 ALARM_S - reference (in S7-400 system and standard functions manual)