Virtual PLC I/O Support
Use this page to choose how a Control Seat Virtual PLC connects to sensors, actuators, remote I/O, existing PLCs, and supervisory systems. Availability is also shown for the selected runtime under Gateway → PLC → Capabilities.
Available connections
| Connection | What you can use it for | Current limits |
|---|---|---|
| FR202 digital I/O | 16 local digital inputs and 16 writable digital outputs | Analog and RTD channels are not yet available as managed Control Seat tags. |
| Raspberry Pi GPIO | Local digital inputs and outputs on supported Raspberry Pi profiles | Use only correctly conditioned 3.3 V GPIO hardware. |
| Modbus TCP | Read and write coils and registers on Ethernet devices | Runs from an enrolled edge or on-premises runtime. |
| Modbus RTU | Read and write serial devices and multidrop networks | Requires a compatible serial port and correct RS-485/RS-232 wiring. |
| Modbus TCP server | Expose selected Control Seat tags to Modbus clients | Available on edge runtimes. |
| OPC UA client | Read, write, and subscribe to values from an OPC UA server | OPC UA server mode is not available yet. |
| MQTT and Sparkplug B | Exchange tags with brokers and Sparkplug systems | Broker access and topic permissions must be configured separately. |
| EtherNet/IP explicit messaging | Read and write supported atomic tags in a Logix controller | This is not a Class-1 scanner and cannot control an EtherNet/IP remote-I/O rack. |
| DNP3 | Read static binary/analog inputs and operate supported binary outputs | Event streaming, secure authentication, time sync, and analog outputs are not available. |
| S7 server | Let compatible Siemens clients read and write bounded data blocks | Client mode is not available. |
| HTTP polling | Map values from REST endpoints into Control Seat tags | Timing follows the configured polling interval. |
Cloud workspaces configure and monitor these connections. Plant-network and serial traffic runs on the enrolled edge or on-premises runtime, so field devices do not need to be exposed to the public internet.
Not currently supported
The following cannot be used for cyclic remote-I/O control today:
- EtherNet/IP Class-1 scanning;
- PROFINET IO Controller;
- PROFIBUS DP master;
- EtherCAT master; and
- OPC UA server mode.
Do not select a device merely because its connector resembles Ethernet or serial. The device and runtime must support the same industrial protocol and role.
Remote-I/O choices today
For new remote I/O, use a Modbus TCP or Modbus RTU coupler. This includes many Wago, Turck, and Beckhoff Modbus products. Allen-Bradley POINT I/O and FLEX I/O require EtherNet/IP Class-1 scanning and are not currently supported as remote I/O racks.
Control Seat can still exchange ordinary tags with existing Logix controllers through explicit EtherNet/IP messaging. That is integration with the existing PLC, not ownership of its I/O rack.
Scan and connection timing
Field connections update tags on their own polling or subscription schedule. At the beginning of each PLC scan, the program captures one consistent snapshot of those tags. Every input used in that scan comes from the same snapshot, but its age depends on the field connection's update rate.
Choose a polling rate that fits the process, and verify the complete path from physical input through the PLC task to physical output during commissioning.
Fault behavior
Bad-quality inputs can either retain their last good value or fault the program. Standard PLC applications can choose hold-last, a typed safe value, or program fault for each output after repeated write failures. Separately scheduled PROGRAM projects currently hold last and retry.
Review PLC Timing and Fault Behavior before commissioning, and keep safety functions within the independent hardware described by the PLC Safety Boundary.
Hardware qualification
Software support does not prove compatibility with every vendor, firmware version, wiring arrangement, or network design. Confirm the exact devices and failure behavior on the physical system before using them in a pilot or production process.