Modifying CP 443-1 Time Synchronization Mode and Download in RUN (CiR) Restrictions

Modifying the Time-of-Day Synchronization mode of a CP 443-1 communications processor in STEP 7 HW Config (e.g. from 'From station to LAN' to 'Automatic') is NOT supported via Configuration in RUN (CiR). In a standalone automation station, downloading this modified hardware configuration strictly requires stopping the CPU (CPU STOP). In a fault-tolerant CPU 410-5H redundant pair, the update can be executed in RUN only if redundant system coupling is fully established. Downloading HW Config always downloads the entire hardware configuration database, overwriting all station parameters rather than downloading changes only.

Hardware Configuration Download Rules: CiR vs Mandatory CPU STOP

In SIMATIC PCS 7, the Configuration in RUN (CiR) facility permits modifying specific hardware parameters—such as adding distributed ET 200M/ET 200SP stations, adding modules, or activating spare channels—without stopping the CPU.

However, CiR is bounded by strict architectural constraints. Low-level bus parameters, central controller rack components, and communications processor (CP) protocol operating modes are excluded from CiR because re-initializing their firmware requires dropping hardware interrupts.

Why Communications Processor Time Synchronization Cannot Use CiR

The Time-of-Day Synchronization parameter on the CP 443-1 (6GK7443-1EX30-0XE0) configures whether the module transmits or forwards SIMATIC time frames across the Industrial Ethernet backplane:

Switching mode from From station to LAN to Automatic alters the internal clock master/slave arbitration logic.
This fundamentally restructures the CP's backplane synchronization interrupt service routines.
Because the CP firmware must reboot its time management stack, STEP 7 rejects any attempt to download this change via CiR.
In a single (non-redundant) controller, downloading HW Config generates the mandatory dialog: The CPU must be stopped to perform the download.

HW Config Download Scope: Entire Station Overwrite Policy

A critical misunderstanding among automation technicians concerns the scope of HW Config downloads:

No 'Changes Only' for Hardware: Unlike CFC charts which support downloading incremental logic changes (Changes only), STEP 7 HW Config always downloads the entire hardware configuration database.
Any other hardware modifications previously made in the offline project by other engineers (e.g. altered I/O addresses, modified watchdog times, or added racks) will be transferred simultaneously, overwriting running controller parameters.

Redundant OS Server Desynchronization After Backup Restores

When a redundant OS Server fails and is restored from an older backup image:

Tag and Screen Divergence: The restored server reflects the older backup timestamp and database schema, causing screens to differ from the running partner server.
Correct Synchronization Sequence:
- Never download to both servers simultaneously.
- Download the current OS project from the Engineering Station to the restored server (Server 1).
- Activate WinCC Runtime on Server 1 and wait for WinCC Redundancy to complete historical archive synchronization.
- Verify that process alarm screens on both servers display identical tag values before testing switchover.

Comparison of Hardware Modification Download Requirements

The table below contrasts download requirements across different hardware modifications:

| Hardware Modification | CiR Capable in Single AS | Redundant AS 410-5H Execution | CPU Stop Mandatory |
|---|---|---|---|---|
| Add ET 200M / ET 200SP I/O Module| Yes (If CiR object present) | Download in RUN (Bumpless) | No |
| Activate Unused Analog Channel | Yes | Download in RUN (Bumpless) | No |
| Modify CP 443-1 Time Sync Mode | No | Requires Redundant OS/AS switchover | Yes (For single AS) |
| Change Controller IP / Subnet | No | Requires Redundant OS/AS switchover | Yes (For single AS) |
| Modify PROFIBUS DP Baud Rate | No | Requires planned plant shutdown | Yes (Interrupts all slaves) |

Verification

Verify time synchronization and controller health following download:

Following the authorized CPU restart (or redundant switchover), check the CPU front LEDs: confirm RUN is solid green.
Open PLC > Diagnostic/Setting > Module Information for the CP 443-1.
In the Time-of-Day Synchronization tab, confirm that the operating mode shows Automatic and reports Synchronized.
Check the CPU diagnostic buffer; verify event Time synchronization established is logged.
In WinCC OS Runtime, verify that all incoming alarms carry accurate, synchronized timestamps matching the plant master clock.

Limitations and Operational Precautions

Observe the following safeguards when executing hardware downloads:

Offline/Online Comparison: Always perform a complete offline/online comparison before downloading HW Config to ensure no unauthorized hardware parameter changes are transferred.
Plant In-Run Constraints: If the controller is a single non-redundant CPU operating a continuous process, the hardware download must be scheduled during a plant outage.
Redundant System Health: In redundant CPU 410-5H systems, verify that both CPUs are in redundant RUN mode and the sync links are healthy before executing redundant hardware updates.

Engineer FAQ

Can CP 443-1 time synchronization mode be downloaded without stopping a single CPU?

No. Communications processor protocol settings and time synchronization modes are not supported by Configuration in RUN (CiR). In a single controller, the CPU must be placed in STOP.

Does downloading HW Config overwrite only the parameters I changed?

No. Downloading HW Config always downloads the entire station configuration database, completely overwriting all hardware settings with the offline project data.

Why do screens on redundant OS Server 1 differ from Server 2 after restoring a backup?

Because restoring a backup image restores the older project version. The restored server must receive a fresh OS project download from the Engineering Station and synchronize its runtime archives with Server 2.