PROFINET to CC-Link IE FB Gateway for Siemens PLC & Mitsubishi Servo

Project Background and Integration Challenge

A production line for decoiling, leveling, feeding, stamping, and stacking was originally commissioned in 2018. The control system featured a Siemens S7-1516-3 PN/DP PLC, with field I/O and 15 G120 inverters communicating over PROFINET IRT at a cycle of 28 strokes per minute. When the equipment department selected Mitsubishi HG-KR series low-inertia motors with MR-J4-B servo drives, a major incompatibility emerged. The drives natively support CC-Link IE Field Basic (up to 4 Mbps, minimum station cycle 1.7 ms), while the PLC only speaks PROFINET. Replacing the entire PLC with a Mitsubishi iQ-R series would have required at least three weeks of downtime and cost approximately $65,000, which production management rejected. The only viable path was a protocol gateway.

Gateway Selection and Network Topology

After evaluating four gateway vendors, an industrial protocol converter with CC-Link IE FB conformance Class A certification (test report CLPA-2025-09-18-07) was chosen. This device acts as a PROFINET IRT slave and a CC-Link IE FB master, with a minimum forwarding delay of 250 µs. It features dual Ethernet ports supporting MRP ring redundancy and comes with a GSDML file for seamless integration into TIA Portal.

Hardware Wiring and Grounding

PROFINET Side

The gateway provides two RJ45 ports supporting MRP. In this project, Port2 was looped back to the switch to form a fiber ring under 50 meters. If any cable is damaged by press vibration, the recovery time is under 200 ms, with zero impact on the 4 ms servo cycle.

CC-Link IE FB Side

Gateway Port1 (RJ45) connects to a Hirschmann switch, then to the CN11 port on each MR-J4-B drive. The topology is a bus with station numbers 1–24, each supporting 256 bytes input and 256 bytes output, totaling 6 kB of cyclic data. The refresh cycle is 1 ms, with the gateway broadcasting refresh frames to maintain real-time servo current loop (16 kHz) and speed loop (4 kHz).

Grounding

The gateway’s metal housing is single-point grounded to the cabinet PE bar to avoid potential differences between PROFINET and CC-Link IE FB. A 6 mm² yellow-green wire connects the six servo drive PE terminals in a grid pattern, ultimately bonded to the press frame ground with less than 1 Ω resistance.

Software Configuration Steps

TIA Portal Setup

1. Import the GSDML file (V2.4) and drag the gateway into the PROFINET network. Set device name “CCLK-Master”, IP 192.168.1.20, update time 2 ms, data length 64 bytes input / 64 bytes output.
2. In the device view, create 6 slots for axis mapping: Slot 1 = Axis 1 (8 Byte I / 8 Byte Q), Slot 2 = Axis 2, etc. This keeps PLC logical addresses contiguous for easy FOR loop programming.
3. After download, use online diagnostics to confirm 2 ms cycle with no packet loss and network load at 11%.

MR Configurator2 Settings

1. Set station numbers 2–7, baud rate 4 Mbps, mode “absolute position + speed feedforward”, electronic gear 1048576 pulse/rev, ball screw pitch 10 mm (1 µm = 0.104 pulse).
2. Configure station 2 as the electronic cam master, stations 3–7 as slaves. The cam curve uses 4096 points over 360°, driven by a press encoder (720 ppr) via a 1:2 timing belt.

Gateway Configuration Tool

1. Connect via USB-C, open the configuration software, read firmware (hardware version V2.3).
2. In the PN→CCLK mapping table, map PLC output bytes QW0–QW63 to CC-Link IE FB master RWw0–RWw31, and RWr0–RWr31 to PLC input bytes IW0–IW63.
3. Enable clock synchronization so the gateway multiplies the PROFINET 2 ms beat to generate a 1 ms CC-Link IE FB sync interrupt, keeping jitter under 50 µs.
4. After writing parameters and restarting, the green RUN LED stays on, and the LNK LED flashes every 100 ms, indicating the master is polling all 6 slaves.

PLC Program Development Highlights

• Use the Siemens LAcyc library with “ReadWriteRecord” to transfer 64 bytes of user data to DB100 in one operation, reducing I/O access.
• Electronic cam calculations run in a 2 ms isochronous interrupt OB61. The master angle is read via a high-speed input (TM PosInput 2 × 24 V differential) with 0.088° resolution.
• Servo commands: first write target position (4 bytes), then control word 6040h (enable, start, emergency stop), and finally trigger a “sync write” bit to update all 6 axes simultaneously.
• Fault bits are polled every 1 ms. If any axis alarms, the PLC cuts the press clutch air pressure within 10 ms and switches the cam curve to a “safe return” segment to prevent die crashes.

Performance Results and Benefits

The protocol gateway delivered a forwarding delay of 250 µs with zero packet loss, enabling the Siemens PLC and Mitsubishi servos to work together as if they were a single brand. The solution preserved the existing PROFINET infrastructure while leveraging the cost-effective electronic cam functionality of the Mitsubishi drives. Key outcomes included:

This approach is applicable to many mixed-vendor environments where real-time motion control is required. By selecting a certified gateway with low latency and robust diagnostics, system integrators can avoid costly PLC replacements and minimize downtime.