Siemens S7-1500 and G120C Drive: Simplest Communication Setup
When integrating a Siemens S7-1500 PLC with a G120C drive, many engineers look for the most straightforward communication method that still delivers reliable performance. The answer is almost always PROFINET with standard telegrams. This approach eliminates complex wiring, reduces commissioning time, and provides seamless access to drive parameters.
Key Takeaway:
Using PROFINET with Telegram 1 or Telegram 20 is the simplest way to control a G120C from an S7-1500. No additional hardware is needed—just an Ethernet cable and TIA Portal configuration.
Why PROFINET is the Preferred Choice
PROFINET is an industrial Ethernet standard that offers deterministic communication, high speed, and easy integration. For the S7-1500 and G120C combination, it provides:
- Plug-and-play connectivity – The G120C has a built-in PROFINET interface (two RJ45 ports).
- Standardized telegrams – Predefined process data structures simplify control and feedback.
- Diagnostics and parameter access – Read/write drive parameters over the same network without extra cables.
- Scalability – Easily add more drives or I/O devices on the same network.
Hardware Requirements
You only need a few components to establish communication:
| Component | Specification | Notes |
|---|---|---|
| S7-1500 CPU | Firmware V2.0 or higher | Any model with PROFINET port (e.g., CPU 1511-1 PN) |
| G120C Drive | PROFINET variant (e.g., 6SL3210-1KE…) | Check the MLFB for built-in PN interface |
| Ethernet Cable | CAT5e or higher, shielded | Standard RJ45 connectors |
| TIA Portal | V15 or later | Includes required GSDML files |
Step-by-Step Configuration in TIA Portal
Follow these steps to set up the communication. The process is straightforward and typically takes less than 15 minutes once you are familiar with the tools.
1. Create a New Project and Add Devices
Open TIA Portal, create a new project, and add your S7-1500 CPU. Then, in the network view, drag and drop the G120C drive from the hardware catalog (under “Other field devices > PROFINET IO > Drives > Siemens AG > SINAMICS”).
2. Assign the Drive to the PLC Network
Connect the G120C to the same PROFINET subnet as the PLC. Assign a unique device name (e.g., “g120c-drive1”) and IP address (e.g., 192.168.0.2). Make sure the IP is in the same range as the PLC.
3. Select the Telegram
In the device view of the G120C, go to the “Telegram configuration” slot. For basic speed control, choose Standard telegram 1, PZD-2/2. This gives you two process data words (control word and speed setpoint) in both directions. For more advanced functions like positioning, you might use Telegram 20 or 352.
Telegram 1 Data Structure:
- PLC → Drive: Control word (STW1), Speed setpoint (NSOLL_A)
- Drive → PLC: Status word (ZSW1), Actual speed (NIST_A)
4. Configure the Drive Parameters
On the G120C, set the command source to PROFINET. This is typically done via the BOP (Basic Operator Panel) or by setting p0015=7 (PROFINET) and p0922=1 (Telegram 1). You can also do this through TIA Portal online access.
5. Program the Control Logic
In the PLC program, you can now directly access the drive’s I/O addresses. For example, if the telegram starts at IW256 and QW256, you can use move instructions to send the control word (e.g., 047E hex for run) and speed setpoint (e.g., 4000 hex for 100% speed).
Common Control and Status Words
Understanding the basic control and status words is essential for troubleshooting. Here are the most frequently used values:
| Control Word (STW1) | Value (Hex) | Description |
|---|---|---|
| 047E | Run command | Enables the drive, no faults |
| 047F | Run with enable | Same as above, often used after fault reset |
| 04FE | Fault acknowledge | Resets a fault condition |
| 047C | Stop (OFF1) | Normal stop with ramp-down |
Troubleshooting Tips
Even with a simple setup, issues can arise. Here are common problems and solutions:
- Drive not found on network: Check the device name and IP address. Use the “Accessible devices” function in TIA Portal to verify.
- No communication (BF LED flashing): Ensure the PROFINET cable is connected and the device name matches the configuration.
- Drive does not start: Verify the control word bits (especially bit 10 for PLC control) and that the drive is in “Ready” state (status word bit 0 = 1).
- Speed setpoint not working: Check the normalization: 4000 hex = 100% of reference speed (p2000).
Advantages Over Other Methods
While you could use analog signals or USS protocol, PROFINET offers clear benefits:
| Method | Wiring Complexity | Data Access | Diagnostics |
|---|---|---|---|
| PROFINET | Single cable | Full parameter access | Extensive, built-in |
| Analog I/O | Multiple wires | Limited to speed/feedback | None over network |
| USS (RS485) | 2-wire bus | Parameter access, slower | Limited |
For most applications, starting with Telegram 1 is the quickest path to a functioning drive system. As your needs grow, you can easily switch to a more feature-rich telegram without changing the physical setup.
Pro Tip:
Use the “SINAMICS Startdrive” software integrated into TIA Portal for guided commissioning. It simplifies parameterization and provides a graphical interface for drive configuration.
By following this guide, you can establish a robust and simple communication link between an S7-1500 and a G120C drive, forming the backbone of many industrial automation control systems. Whether you are designing a new electrical control panel or retrofitting an existing one, this method ensures reliable motor control with minimal effort.
