Can Ignition's S7-300 Driver Reach a PLC via NetLink Lite?

Ignition's built-in Siemens S7-300 driver will not reach a CPU through a Helmholz NetLink Lite MPI-to-Ethernet adapter. The NetLink Lite does not terminate RFC1006. It uses its own gateway protocol, and on the host side that protocol needs vendor driver software or a third-party driver written for it. Changing the Ignition device port to match the adapter's listening port does not help, because the port is not the mismatch. The protocol on that port is.

You have two working paths. The first is an adapter that supports RFC1006, either through a Helmholz firmware update or the successor product. The second is an OPC server that already speaks the NetLink protocol, with Ignition connected to it as a client. The sections below build either path in order, with a check at the end of each step.

RFC1006 Transport Requirement of the Built-in S7 Driver

The term RFC1006Siemens Ethernet CPs, PN CPUs and RFC1006-capable gateways listen on TCP port 102. The S7 communication PDUs ride inside that transport. On an S7-300 CPU this is typically rack 0, slot 2. After that the driver negotiates the S7 PDU size.

An MPI gateway can serve this driver only if it does three things:

• Accept the RFC1006 connection request on the Ethernet side.
• Translate it into an MPI connection to the CPU's MPI station address.
• Relay the S7 PDUs in both directions.

The adapter's ping and web page can look healthy while the device status never leaves the connecting state.

Check 1: from the Ignition gateway host, run Test-NetConnection <adapter-IP> -Port 102 in PowerShell.

• Expect TcpTestSucceeded : True on an RFC1006-capable adapter.

Gateway Adapter Identification and Protocol Support

MPI-to-Ethernet adapters from different vendors share similar names. Two of them are relevant here:

• Hilscher NetLINK: other Ignition installations report working connections with this adapter.
• Helmholz NetLink Lite: this is the adapter in this installation. It has been out of production for some years, and it was designed to work with Siemens engineering software through a special host-side driver.

Reports of success with one adapter do not transfer to the other. Identify the exact unit before changing any Ignition settings.

Check 2: read the adapter label and the web or configuration page for model and firmware. Record both. Expect a clear identification of NetLink Lite versus a successor or third-party unit. You need that data when you contact Helmholz about RFC1006 firmware support.

Port 1099 and Why Matching It Fails

In this installation, a second HMI uses Kepware and communicates through the NetLink Lite on port 1099. Setting the Ignition S7-300 device to port 1099 produced no communication. That result is expected.

Port 1099 carries the adapter's own framing. Kepware works because it includes a driver model that implements that framing. When Ignition's driver sends an RFC1006 connection request into that socket, the adapter rejects it or ignores it.

Leaving an S7 device pointed at a non-RFC1006 port is wrong practice. The driver retries without end, and some adapters allow only a small number of host sessions. Retries can hold a session slot that the working Kepware HMI needs.

Check 3: after you revert or disable the failed Ignition device, confirm that the existing Kepware HMI still updates. Expect Kepware tag quality Good and no new connection errors in its event log.

Path A: RFC1006-Capable Adapter and Direct Ignition Device

Use this path when Helmholz supplies firmware that adds RFC1006 to the unit, or when you replace it with the successor adapter, which supports RFC1006.

1. Contact Helmholz with the model and firmware from Check 2. Ask whether an RFC1006-capable firmware exists for the NetLink Lite. If it does not, specify the successor unit.
2. Set the adapter's IP, subnet mask and gateway for the Ignition network segment.
3. Configure the adapter's MPI side to match the CPU's MPI bus: baud rate, highest station address, and the adapter's own free MPI address. Read the actual values from the CPU's MPI interface properties in the hardware configuration. Do not assume defaults.
4. Map the adapter to the CPU's MPI station address. The adapter's configuration tool determines whether you enter this in the adapter or through the rack/slot fields.
5. In Ignition, create a Siemens S7-300 device. Set the hostname to the adapter IP and the port to 102. Set rack and slot to match the CPU position, typically rack 0, slot 2 on an S7-300.
6. Save and watch the device status.

Check 4: expect the device status to read Connected within a few seconds. If it cycles between Connecting and Disconnected, check three things in this order:

• The rack and slot values.
• The MPI station address the adapter targets.
• Free connection resources on the CPU.

An S7-300 CPU has a limited pool of connection resources. The existing HMI, the programming device and the new gateway session all draw from it. Read the current usage in the CPU module diagnostics under communication.

Path B: Kepware as OPC Server Between Ignition and the NetLink Lite

Use this path when the adapter must stay in place. Kepware already talks to the CPU through the NetLink Lite on port 1099, so Ignition consumes Kepware's tags as an OPC client. This installation named OPC-COM as the fallback, which is the classic OPC DA route through Ignition's OPC-COM module. If the Kepware version in use exposes an OPC UA endpoint, Ignition's native OPC UA client connection is an alternative. It avoids DCOM configuration when Kepware and Ignition run on different hosts.

1. In Kepware, confirm that the channel and device for the S7-300 through the NetLink Lite work, with tags reading Good quality.
2. Add the tags Ignition needs to that device, or reuse the existing ones. Keep the scan rates sensible to limit MPI bus load. MPI throughput is far below Ethernet throughput, and every added tag competes with the existing HMI.
3. In Ignition, create the OPC connection: OPC-COM for DA, or OPC UA for Kepware's UA endpoint. For a UA connection, accept the certificate on both sides.
4. Browse the Kepware server from Ignition and drag the required tags into the tag provider.

Check 5: expect the Ignition OPC connection status to read Connected. Browsed tags should show quality Good with values that match Kepware's Quick Client. If quality is Bad or the connection is unavailable on OPC-COM across hosts, suspect DCOM permissions or the Windows firewall before suspecting the PLC path.

End-to-End Verification

Run these checks after either path is in place.

1. Check 6, network reach: ping the adapter from the Ignition host. Expect replies with no loss.
2. Check 7, transport: for Path A, run Test-NetConnection to port 102 and expect True. For Path B, confirm Kepware's channel shows no communication errors on its NetLink connection.
3. Check 8, read path: pick a free-running value in the CPU, such as a clock byte or a counter in a data block, and subscribe to it in Ignition. Expect the value to change at the rate the PLC updates it, with quality Good.
4. Check 9, write path: on a scratch data block word that the program does not use, write a known value from Ignition. Read it back online in the Siemens engineering software. Expect an exact match.
5. Check 10, coexistence: with Ignition connected, confirm that the existing Kepware HMI still updates, and that the programming software can still go online through its usual route. Expect no dropped sessions and no new connection-resource errors in the CPU diagnostic buffer.
6. Check 11, recovery: power-cycle the adapter while Ignition runs. Expect the Ignition device or OPC connection to drop, then return to Connected without manual intervention once the adapter finishes booting.

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