Troubleshooting High-Precision Time Stamping with IMDRV_TS and EventTs in SIMATIC PCS 7 V9.0

In SIMATIC PCS 7 V9.0 base release, high-precision time-stamping (1 ms Sequence of Events) alarms failing to appear on the WinCC Operator Station is caused by a known software regression in driver block IMDRV_TS (FB119) within PCS 7 Basis Library V9.0. While the ET 200M IM 153-2 interface module and EventTs (FB1212) correctly capture edge transitions, the base V9.0 release of IMDRV_TS fails to unpack diagnostic data records from the IM buffer. Siemens corrected this issue in PCS 7 Basis Library V9.0 Update 1 and subsequent service packs. The permanent solution is to install Basis Library V9.0 Upd1 (or higher), update block types in the chart folder, and recompile CFC.

Architecture of 1 ms High-Precision Time Stamping in PCS 7

In critical process and power generation applications, determining the exact root cause of a plant trip requires Sequence of Events (SoE) recording with 1-millisecond resolution. SIMATIC PCS 7 implements high-precision time stamping through a tightly synchronized hardware and software toolchain:

Clock Synchronization Master: A central master clock (e.g., SICLOCK TC 400 or NTP time server) synchronizes the S7-400 AS CPU and distributed I/O stations with sub-millisecond precision.
ET 200M IM 153-2 High Feature: The IM 153-2 communication module receives time telegrams across PROFIBUS DP and synchronizes its internal timer.
Digital Input Module (6ES7321-7BH01-0AB0): Dedicated 16-channel DI modules detect rising and falling signal edges via hardware interrupts, stamping each event with local 1 ms timestamps and buffering them in the IM 153-2 ring buffer.
Driver Block IMDRV_TS (FB119): Automatically placed into the @ system charts by the Driver Generator, IMDRV_TS reads data records (DS 100/101) from the IM 153-2 buffer.
Message Block EventTs (FB1212): Formats the time-stamped events and transmits them via ALARM_8P to WinCC Alarm Logging.

The IMDRV_TS V9.0 Driver Evaluation Defect Explained

During initial validation of SIMATIC PCS 7 V9.0, engineers noticed that rapidly toggling digital inputs on a verified time-stamped rack (IM 153-2 + 6ES7321-7BH01-0AB0) generated zero alarms in the WinCC AlarmControl window, despite EventTs.TimeStampOn = true.

Substituting the IMDRV_TS block with the older version (V7.7 from Basis Library V8.1) immediately restored flawless alarm delivery. Diagnostic investigation confirmed an internal defect in IMDRV_TS V9.0:

Software ComponentVersionBehavior on Digital Edge TransitionSystem StatusIMDRV_TS (Basis Library V8.1)V7.7Reads DS100, evaluates buffer pointers, triggers EventTsFully functional (1 ms SoE active)IMDRV_TS (Basis Library V9.0 Base)V9.0Buffer evaluation loop terminates prematurely; drops recordsDefective (Alarms Lost)IMDRV_TS (Basis Library V9.0 Upd1+)V9.0.1+Corrected buffer pointer handling and record parsingFully Resolved (Official Patch)

In the initial V9.0 build, a pointer calculation error during the evaluation of multi-event data records caused the block to acknowledge the buffer in the IM 153-2 without forwarding message frames to the EventTs block.

Step-by-Step Resolution and Library Patch Workflow

To resolve the time-stamping failure permanently without reverting to legacy libraries, execute the following update procedure:

Download Basis Library Update: Access Siemens Industry Online Support (SIOS) and download the latest update package for SIMATIC PCS 7 Basis Library V9.0 (Update 1 or higher, or apply PCS 7 V9.0 SP1).
Install Update on Engineering Station: Close all SIMATIC Manager instances and install the update setup package on the ES.
Update Block Types in Master Data Library: Open your central Master Data Library. Copy the updated IMDRV_TS (FB119) and EventTs (FB1212) blocks from the system library (PCS 7 Basis Library V9.0) into the Master Data Library block folder.
Propagate Block Types to AS Programs: In SIMATIC Manager, select the Master Data Library block folder, right-click and select Options -> Charts -> Update Block Types.... Select the target AS automation stations and execute the update.
Recompile CFC Program: Open any CFC chart. Select Chart -> Compile -> Chart as Program. Enable the option 'Generate module drivers' and select Changes Only. The driver generator updates the @ system charts with the new block version.
Download Changes to AS Controller: Perform a Download Changes in RUN to the target S7-400 CPU.

Verification

Verify that high-precision time stamping operates reliably through these diagnostic procedures:

Module Diagnostic Buffer Inspection: In HW Config, double-click the IM 153-2. Verify that Time synchronization is active and that zero time-stamp synchronization errors appear in the module diagnostic buffer.
Simulate Fast DI State Changes: Connect a field test switch to channel 0 of the 6ES7321-7BH01-0AB0 card. Toggle the switch rapidly 5 to 10 times.
WinCC Alarm Logging Verification: Open the WinCC OS AlarmControl window. Confirm that every individual state transition appears with message class 'Alarm' or 'Process Message' and displays a unique timestamp with millisecond precision.

Limitations and Operational Precautions

When implementing 1 ms time stamping in PCS 7, observe these hardware and architecture constraints:

Module Compatibility: Only designated digital input modules (such as 6ES7321-7BH01-0AB0) support hardware time-stamping. Standard digital input modules (6ES7321-1BL00-0AA0) do not contain the local edge-detection ASIC.
IM 153-2 Redundancy Coupling: In redundant ET 200M configurations, both IM 153-2 modules must be identical firmware revisions and both must be synchronized via the active backplane bus (6ES7195-7HD10-0AA0).
Never Mix Unchecked Block Versions: Do not manually copy individual blocks from older PCS 7 releases (e.g. V8.1 into V9.0) as a long-term fix. Mixing library versions breaks Driver Generator consistency during future full compilations.

Engineer FAQ

Why did substituting IMDRV_TS V7.7 work if PCS 7 V9.0 requires V9.0 blocks?

The basic internal interface between IMDRV_TS and EventTs remained largely backward compatible. The older block lacked the pointer bug, so it functioned temporarily. However, relying on mixed block versions causes compilation errors when generating module drivers.

Does 1 ms time stamping work over PROFINET in PCS 7 V9.0?

Yes. On PROFINET architectures, high-precision time stamping is achieved using ET 200SP HA or ET 200M with IM 153-4 PN and isochronous real-time (IRT) clock synchronization.

What is the maximum message burst rate supported by IM 153-2?

The IM 153-2 ring buffer holds up to 128 time-stamped edges. If a massive electrical chatter exceeds buffer capacity, an explicit 'Buffer Overflow' diagnostic alarm is transmitted to WinCC.