6ES7901-3CB30-0XA0 SIMATIC S7-200
The Siemens SIMATIC S7 6ES7901-3CB30-0XA0 is a PC/PPI (Point-to-Point Interface) multi-master cable designed for use with the SIMATIC S7-200 series of programmable logic controllers. This cable serves as the programming and communication interface between a PC and S7-200 CPUs, enabling program upload, download, and online monitoring via the STEP 7-Micro/WIN software environment. It belongs to the broader SIMATIC S7-200 accessory ecosystem and is an essential tool for commissioning, diagnostics, and maintenance of S7-200 installations.
The 6ES7901-3CB30-0XA0 connects a standard RS-232 serial port on the PC side to the PPI port on the S7-200 CPU, supporting multi-master communication on the MPI/PPI bus. The cable incorporates an integrated RS-232 to RS-485 signal converter, allowing reliable communication over the PPI protocol without requiring an additional adapter. It supports baud rates up to 187.5 kbps and is compatible with all S7-200 CPU variants that feature a standard PPI port. The cable is powered directly from the RS-232 interface, requiring no external power supply.
This cable is primarily used in small-scale industrial automation applications where S7-200 PLCs are deployed, including machine control, building automation, conveyor systems, and process control panels. It is an indispensable tool for system integrators, maintenance engineers, and OEM machine builders who need to program or troubleshoot S7-200 controllers in the field or workshop. Its compact, portable form factor makes it well suited for on-site commissioning and diagnostic tasks.
Technical Specifications
| Interface (PC Side) | RS-232 (9-pin D-sub) |
|---|---|
| Interface (PLC Side) | RS-485 / PPI (9-pin D-sub) |
| Communication Protocol | PPI (Point-to-Point Interface), Multi-Master |
| Maximum Baud Rate | 187.5 kbps |
| Signal Conversion | RS-232 to RS-485 |
| Power Supply | Powered via RS-232 interface (no external supply required) |
| Compatible Software | STEP 7-Micro/WIN |
| Compatible PLC Series | SIMATIC S7-200 |
| Cable Type | PC/PPI Multi-Master Cable |
| Series/Product Family | SIMATIC S7-200 Accessories |
| Certifications | CE |
Common Communication and Diagnostic Codes
- No Communication
- STEP 7-Micro/WIN cannot establish a connection to the S7-200 CPU via the cable.
Verify the correct COM port is selected in Micro/WIN. Check that the cable is firmly seated on both the PC RS-232 port and the CPU PPI port. Ensure the baud rate in Micro/WIN matches the CPU PPI port setting. - Wrong Baud Rate
- Communication is intermittent or fails due to a baud rate mismatch between the cable and the CPU.
Set the baud rate in STEP 7-Micro/WIN to match the S7-200 CPU PPI port baud rate (default 9.6 kbps). Adjust the DIP switches on the cable if applicable. - COM Port Not Found
- The PC does not recognize the cable on any COM port.
Check that the RS-232 port on the PC is functional. If using a USB-to-RS-232 adapter, ensure the adapter driver is correctly installed and the assigned COM port number is within the range supported by Micro/WIN (typically COM1-COM4). - Timeout Error
- STEP 7-Micro/WIN reports a timeout when attempting to read from or write to the CPU.
Check cable connections and ensure the S7-200 CPU is powered and in a ready state. Reduce cable length if using an extension. Verify no other application is occupying the COM port. - Multi-Master Conflict
- Communication errors occur when multiple masters are present on the PPI network.
Ensure that the cable is configured for multi-master mode if other devices are on the bus. Check network addresses for conflicts and verify that only one programming device is actively communicating at a time. - Program Download Failed
- Download of the user program to the S7-200 CPU is interrupted or fails to complete.
Confirm the CPU is in STOP mode before initiating a download. Check for sufficient memory in the CPU. Re-seat the cable connections and retry the download operation.
Frequently Asked Questions
Is the 6ES7901-3CB30-0XA0 compatible with S7-300 or S7-400 PLCs?
No, this cable is designed specifically for the SIMATIC S7-200 series. For S7-300 and S7-400 PLCs, a separate MPI or PROFIBUS programming cable is required.
Does this cable require an external power supply?
No, the 6ES7901-3CB30-0XA0 draws its operating power directly from the RS-232 serial port of the PC, so no external power supply is needed.
Can this cable be used with a USB-to-RS-232 adapter?
Yes, it can be used with a USB-to-RS-232 adapter, but compatibility is not guaranteed with all adapters. It is recommended to use a high-quality adapter with a verified chipset (such as FTDI or Prolific) and to ensure the virtual COM port number is within the range supported by STEP 7-Micro/WIN.
What software is required to use this cable?
The cable is used with Siemens STEP 7-Micro/WIN programming software, which is the standard development environment for the SIMATIC S7-200 PLC family.
What is the maximum communication baud rate supported by this cable?
The cable supports PPI communication at baud rates up to 187.5 kbps, with the default S7-200 PPI port baud rate being 9.6 kbps.
Troubleshooting
STEP 7-Micro/WIN cannot find the PLC after cable connection
Check the COM port assignment in Micro/WIN communication settings. Verify the cable is connected to the correct RS-232 port on the PC and the PPI port on the CPU. Confirm the S7-200 CPU is powered on.
Set the correct COM port in Micro/WIN under 'Set PG/PC Interface'. If using a USB-to-RS-232 adapter, check Device Manager for the assigned COM port and ensure it is within COM1-COM4. Restart Micro/WIN after making changes.
Intermittent communication dropouts during online monitoring
Inspect the cable connectors for loose or damaged pins. Check for electromagnetic interference sources near the cable. Verify the baud rate setting is stable and consistent between the PC and CPU.
Reseat both cable connectors firmly. Reduce cable length or route the cable away from high-voltage wiring. Lower the communication baud rate in Micro/WIN if dropouts persist.
Program download aborts partway through
Check that the CPU is in STOP mode and that the available program memory in the CPU is sufficient for the project. Verify the cable connection has not been disturbed during the download.
Switch the CPU to STOP mode before initiating the download. Clear the CPU memory if necessary and retry. Ensure the cable connectors are secure throughout the download process.
PC does not detect the RS-232 cable at any COM port
Test the RS-232 port on the PC with another known-working device. If using a USB-to-RS-232 adapter, check that the driver is installed and the device appears in Device Manager without errors.
Replace or repair the RS-232 port if faulty. Install or reinstall the USB-to-RS-232 adapter driver. Try a different USB port on the PC and confirm the COM port number assigned to the adapter.
Cable appears functional but CPU does not respond to commands
Verify the PPI port address and baud rate configured in the S7-200 CPU match the settings in STEP 7-Micro/WIN. Check that no other master device is actively communicating on the PPI bus.
Use Micro/WIN's 'Search for all baud rates' option to auto-detect the CPU. Disconnect other devices from the PPI bus during programming. Confirm the CPU PPI port is not disabled in the system block configuration.
| Condition | Repair, Used, Refurbished, New in box (sealed) |
|---|
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