Tips & practical notes
Tips and practical notes for operating the S7+ Connector.
This page collects tips and practical notes for operating the S7+ Connector with Siemens S7 controllers via the S7+ protocol. It describes common effects in production environments and the recommended way to handle them.
HMI switches to Transfer Mode
Symptom
While the S7+ Connector is establishing or maintaining an active connection to an S7 CPU, a Siemens HMI (e.g. Comfort Panel, MP277/377) on the same network switches from runtime to Transfer Mode. The panel shows the dialog "Connecting to host..." with a Cancel button.
The machine cannot be operated via the HMI while it is in this state.
Cause
When configured as Engineering Station, the S7+ Connector identifies itself to the S7 CPU as a PG connection using the same connection parameters that WinCC flexible or TIA Portal use. This enables a stable, priority-aligned data connection.
If a Siemens HMI on the same network has Automatic Transfer and Remote Control enabled, the panel reacts to detectable engineering activity in the network and switches to Transfer Mode proactively, assuming an imminent project download. No direct communication between the Connector and the HMI is required to trigger this behavior.
For new S7+ data sources, HMI is the default Connection Type to avoid this effect. Existing data sources still configured as Engineering Station can continue to exhibit the issue.
This effect is caused exclusively by the active S7+ Connector acting as an engineering endpoint in the network. Other ENLYZE tools (e.g. the Flex Configuration Extractor) operate strictly on locally downloaded project files and never communicate with the panel or machine.
Resolution options
There are two ways to resolve this. The right choice depends on whether you want to adjust the Connector configuration or the HMI.
In the connection settings of the data source, the S7+ Connector can be configured to identify itself to the CPU as an additional HMI instead of an Engineering Station. In this mode, the effect does not occur because the panel detects no engineering activity in the network.
Open the data source
In the ENLYZE Manufacturing Data Platform, select the affected S7+ data source.
This option is non-invasive for the machine and prevents the issue from recurring on future reconnects or with additional HMIs added to the network.
Alternatively, the setting can be disabled directly on the panel. This is best practice in production environments anyway, since otherwise any engineering activity in the network can push the panel out of runtime.
With this option, the Connector still runs as an Engineering Station. If additional HMIs exist or are later added to the machine, the same settings must be checked on those panels as well.
Immediate recovery during operation
If the effect is currently active, here is how to bring the panel back into runtime:
Press Cancel in the transfer dialog. The panel returns to runtime operation.
If Cancel does not respond: restart the panel (power cycle). On startup it loads the last valid runtime.
The panel itself is not damaged by entering Transfer Mode.
Pre-install check
Before connecting an S7+ Connector to an S7 CPU with attached HMIs, we recommend the following check:
Are there Siemens HMIs on the network connected to the same CPU?
If yes: the default Connection Type
HMIavoids the effect. We recommend keeping it.If
Engineering Stationis chosen deliberately (e.g. for higher priority): are Automatic Transfer and Remote Control disabled on all affected panels?
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