Connecting Siemens TP1200 Comfort Panel to GE RX3i PLC

1. Problem Definition and System Overview

The migration scenario described in the source material covers a common industrial retrofit problem: a plant wants to replace an end-of-life or unsupported GE Quick Panel HMI (IC754 series) with a current-generation Siemens TP1200 Comfort Panel, while keeping the existing GE PACSystems RX3i controller in service. The RX3i remains the source of truth for I/O, logic, and motion; the new HMI must read and write process variables over the existing Ethernet infrastructure.

The TP1200 Comfort (6AV2 124-1MC01-0AX0 or current 6AV2 124-1MC01-0AX1 variant) is a 12.1-inch widescreen TFT panel with 1280x800 resolution, designed to run on SIMATIC WinCC Comfort, WinCC Advanced, or WinCC Professional under TIA Portal V15.1 through V21. It supports PROFINET, Modbus TCP, OPC UA, and a long list of third-party PLC drivers that allow direct connection to non-Siemens controllers without an external gateway.

The GE (now Emerson) PACSystems RX3i CPU, for example the IC695CPU315, IC695CPU320, or the current IC695CPE330, exposes a built-in Ethernet port that natively speaks SRTP (Service Request Transfer Protocol), Modbus TCP Server, and EGD (Ethernet Global Data). With the IC695ETM001 or IC695PNS001 Ethernet modules, the same controller can be configured as an Ethernet/IP scanner or adapter. This native protocol set is the key to selecting the right WinCC channel.

2. Prerequisites and Required Components

Refer to the official Siemens documentation Communicating with PLCs (Basic Panels, Panels, Comfort Panels, RT Advanced, RT Professional) for the complete driver matrix and version-specific restrictions in TIA Portal V21.

3. Communication Protocol Selection Matrix

For the typical retrofit covered by the source question, Modbus TCP is the most cost-effective path: the RX3i CPU exposes Modbus Server on TCP port 502 with no additional hardware, and the TP1200 ships with a Modbus Master channel that maps discrete, register, input, and holding areas directly into HMI tags.

4. Option 1: Modbus TCP Implementation

Modbus TCP is the lowest-risk option. Both devices speak an open protocol, addressing is straightforward, and the entire configuration can be completed in a single TIA Portal session plus a one-time configuration in PME.

4.1 Enable Modbus Server on the GE RX3i

1. Open the RX3i project in Proficy Machine Edition.
2. Right-click the Ethernet port under Hardware Configuration > Slot 0 (CPU) and select Properties.
3. On the Ethernet tab, set a static IP address, for example 192.168.0.10, subnet mask 255.255.255.0.
4. Open the Protocols sub-tab and enable Modbus/TCP Server. Leave the default TCP port at 502.
5. Click OK and download the configuration to the CPU. A warm restart is not required.

4.2 Configure the Modbus Master Channel in WinCC

1. Open the TIA Portal project containing the TP1200 device.
2. Select the TP1200, then open Connections in the project tree.
3. Right-click and choose Add new connection → driver Modicon Modbus TCP.
4. Set the partner IP to 192.168.0.10 and the partner port to 502.
5. Leave the local port at 0 (auto-assign). Under Connection mode select Active (master).
6. Configure the polling cycle (default 1000 ms is acceptable for most process displays; tighten to 200-500 ms for high-speed alarms).

4.3 HMI Tag Mapping to Modbus Address Ranges

5. Option 2: Ethernet/IP Implementation

Ethernet/IP is a CIP-based protocol widely used in North American plants. The TP1200 includes an Allen-Bradley EtherNet/IP channel that can connect to RX3i controllers configured as Ethernet/IP adapters.

5.1 Enable Ethernet/IP on the GE RX3i

1. Install an IC695ETM001 module in the RX3i backplane (slot 2 or higher) if the CPU port is already used or does not support EIP.
2. In PME, add the ETM001 to the hardware configuration and assign a unique IP, for example 192.168.0.11.
3. Open Properties > Ethernet > Protocols on the module and enable Ethernet/IP Adapter (server) mode.
4. Map the cyclic and explicit assemblies. The most common mapping is:
   - Input Assembly 100 = 32 words of %AI data
   - Output Assembly 101 = 32 words of %R data (writes from HMI)
   - Configuration Assembly 102 = static configuration instance
5. Download to the controller. The ETM001 will advertise over CIP multicast.

5.2 Configure the Allen-Bradley EtherNet/IP Channel in WinCC

1. In TIA Portal, add a new connection with driver Allen-Bradley EtherNet/IP.
2. Set the partner IP to 192.168.0.11.
3. Choose the CPU type Generic EtherNet/IP Scanner.
4. Under Cyclic data, add the input assembly (instance 100, size 32) and output assembly (instance 101, size 32).
5. For data outside the cyclic assemblies, use explicit messaging tags: Read Tag (CIP Service 0x4C) and Write Tag (0x4D) with symbolic names matching RX3i variables.

6. Option 3: OPC UA Server Bridge

When the RX3i already feeds multiple consumers (HMI, historian, MES), an OPC UA server is the most scalable option. The TP1200 includes an OPC UA Client channel in WinCC Advanced and Professional; Comfort runtime supports OPC UA Client as of WinCC V16 Update 3.

1. Install an OPC UA server (Kepware ServerEX 6.x with GE Ethernet driver, Matrikon OPC Server for GE Ethernet, or the PACSystems native OPC UA Server if running firmware 9.40+ on CPE400/CPE330).
2. Import the RX3i tag database from PME. In Kepware, use the GE Ethernet driver and browse the controller's symbolic memory map.
3. Configure the server's endpoint URL, e.g., opc.tcp://192.168.0.20:49320, and create a user account for the TP1200.
4. In TIA Portal, add a connection with driver OPC UA Client, enter the endpoint URL, set security policy to None for testing or Basic256Sha256 for production.
5. Browse the server's address space and drag the desired tags into the HMI tag table.

This approach adds one component (the OPC UA server) and a Windows-class machine, but it also future-proofs the data path for IIoT, MQTT bridges, and cloud connectors.

7. GE RX3i Communication Port Configuration Reference

8. WinCC TIA Portal Driver Configuration Reference

9. Tag Mapping and Register Addressing Examples

The following mapping is a copy-paste-ready reference for a 64-word cyclic exchange. Place this in the WinCC HMI tag table, with acquisition mode set to Cyclic on use.

// Modbus Holding Register 40001-40064 (RX3i %R00001-%R00064)
// Word order: Big Endian (high word at lower address)

HMI_Tag                  Addr    Type      RX3i source
ProcessPressure_PSI      40001   Real      %R00001
ProcessFlow_GPM          40003   Real      %R00003
TankLevel_Pct            40005   Real      %R00005
Motor1_SpeedSetpoint     40007   Real      %R00007
Motor1_SpeedFeedback     40009   Real      %R00009
Valve1_PositionCmd       40011   Real      %R00011
Valve1_PositionFB        40013   Real      %R00013
RecipeNumber             40015   Int       %R00015
BatchCount              40016   Int       %R00016
AlarmWord_Global         40017   Word      %R00017
Heartbeat_Seconds        40018   DInt      %R00018 (2 words)
ShiftID                  40020   Word      %R00020
OperatorName_Word0       40021   Word      %R00021
OperatorName_Word1       40022   Word      %R00022
... (continue to 40064)

10. Network Topology and Cabling

Keep the HMI, controller, and engineering station on the same broadcast domain for the initial commissioning. VLAN segmentation is recommended only after a clean baseline is established, to avoid issues with CIP multicast and EGD broadcasts being filtered at the router.

11. Commissioning and Verification Procedure

1. Physical layer check. Confirm link LEDs on both ports, run a 30-second ping from the TP1200 service menu (Control Panel > Network > Ping) to 192.168.0.10.
2. Protocol enablement verification. In PME, go online with the RX3i and use the Monitor > Ethernet > Connections view to confirm the Modbus Server is bound and listening on port 502.
3. WinCC online test. Right-click the TP1200 in TIA Portal, select Go online, open the HMI tag table, and toggle the Monitor button. Each Modbus tag should show a current value and a status code of OK (green).
4. Forcing test from HMI. Set a writable tag (e.g., Motor1_RunCmd) to 1 from the HMI faceplate. In PME, watch the corresponding %M00001 go TRUE within one polling cycle.
5. Performance test. In the WinCC diagnostics view, observe the channel status. Error count should be zero, and average cycle time should match the configured polling rate within 10%.
6. Loss-of-comms test. Disconnect the Ethernet cable for 10 seconds. The TP1200 should display a connection-loss alarm; reconnect, confirm automatic recovery without restarting the runtime.
7. Project transfer. Compile and download the TIA Portal project to the TP1200. Perform an HMI restart (Control Panel > OP > Reboot) and verify the connection comes up automatically after the panel boots.

12. Troubleshooting Matrix

13. Frequently Asked Questions