Configuring Siemens CP50M0 PROFIBUS DP Master on SIMATIC TDC

Configuring Siemens CP50M0 PROFIBUS DP Master on SIMATIC TDC

The Siemens CP50M0 is the PROFIBUS DP master interface module used in SIMATIC TDC (Technology and Drive Control) racks and in its predecessor platform, SIMADYN D. Despite the modern migration of fieldbus engineering to TIA Portal, hundreds of TDC installations are still in service worldwide and depend on the legacy COMProfibus V5.1 tool, a CP5611 PCI card, and a proprietary Siemens service cable for commissioning and maintenance. This reference explains how the CP50M0 is parameterized, why the COMProfibus Import command does not work for this station type, and the correct Export-DP Master procedure that downloads the configuration into the module over CP5611.

1. CP50M0 PROFIBUS Master Overview in SIMATIC TDC

The CP50M0 is a communications processor module that occupies one slot in the SIMATIC TDC subrack. It provides a single PROFIBUS DP master channel at RS-485, 9.6 kbit/s up to 12 Mbit/s, conforming to EN 50170 Volume 2 (PROFIBUS DP). It communicates with the TDC CPU module (SS52 family) over the backplane and exchanges process data with the application memory in deterministic cycle times.

Inside COMProfibus, the CP50M0 is registered under the master station type Simadyn D SS52 because the firmware image, the bus parameter record layout, and the configuration download protocol were inherited from the SIMADYN D platform. Choosing any other station type (IM308-C, IM180-V3, S5-95U DP/Master) will produce a project that the module rejects.

2. Prerequisites and Required Components

Before attempting any configuration exchange with a CP50M0, the following items must be available.

3. Why CP50M0 Import Fails in COMProfibus

The CP50M0 firmware does not implement the upload protocol expected by COMProfibus for the Import menu path. When the operator opens COMProfibus and selects File → Import..., the tool enumerates the three master types it can read from a live module:

• IM308-C (for S5-135U/155H racks)
• IM180-V3 Master (S7-400 stand-alone DP master)
• S5-95U DP/Master (S5-95U PLC)

CP50M0 is not in this list because the upload protocol used by SIMADYN D SS52 does not expose the binary parameter set in a form that COMProfibus can re-parse. The tool will display the dialog, but selecting any of the three stations produces no response from the module even when the CP5611 is logically linked and the LEDs indicate a healthy parameterization link.

Implications for the field engineer

1. If the original COMProfibus project file exists on a backup medium, restore it and edit that file.
2. If the project file is lost, reconstruct the configuration from the wiring diagram and the I/O address list of the TDC application. The CP50M0 does not retain human-readable documentation of its slaves.
3. Treat any clone or spare module as blank and always download a fresh project before commissioning.

4. Correct Configuration Workflow: Simadyn D SS52

The supported workflow assumes the engineer is creating or editing the project offline and pushing the result into the module.

1. Launch COMProfibus V5.1.
2. From File → New, create a project and select the master station type Simadyn D SS52. The dialog will not offer CP50M0 by name; SS52 is the correct logical target.
3. Open Master → Parameters and set:
   • Bus profile (Standard / User-defined)
   • Baud rate matching the installed slaves
   • Slot time, quiet time, setup time, target rotation time (T_TR)
   • Watchdog and group assignment
4. Add slaves from the GSD catalog (Slave → Insert) and assign I/O bytes per the TDC application interface definition.
5. Save the project as a .pdb file in a versioned folder structure (e.g. \\plant\t-dc\unit-01\cp50m0\pdb\rev07\).

Bus parameter reference

5. Export-DP Master Download Procedure

Once the project compiles cleanly, the configuration is pushed to the CP50M0 by the Export-DP Master command. The dialog wording is historical and does not perform a file export; it initiates a parameter download to the module.

1. In COMProfibus, with the project open, right-click the Simadyn D SS52 master icon in the tree view.
2. Select Export-DP Master.... The download dialog opens.
3. Confirm the CP5611 is selected as the access point (PG/PC interface = CP5611(PROFIBUS)).
4. Connect the service cable between the CP5611 9-pin sub-D and the TDC parameterization port (front X1 of the rack).
5. Switch the CP50M0 to STOP using the toggle switch on the front panel or via the TDC operator panel.
6. Click Start in the Export-DP Master dialog. The progress bar indicates parameter block transfer.
7. Watch the CP50M0 front-panel LEDs:
   • STOP LED solid during transfer
   • SF LED flashing during parameterization
   • Successful end: STOP LED off, RUN LED green
8. When the dialog reports Transfer OK, switch the module back to RUN and verify DP slaves come online.

Failed-transfer matrix

6. CP5611 Interface Installation and Driver Setup

The CP5611 (Siemens part number 6GK1561-1AA01) is a PCI card that provides both MPI and PROFIBUS interfaces to the engineering PC. COMProfibus V5.1 cannot operate without a properly installed CP5611 driver layer.

1. Insert the CP5611 in a free PCI slot and boot Windows.
2. Install SIMATIC NET PC Software V6.4 SP4 or V7.1 (matching COMProfibus V5.1 compatibility matrix).
3. In Set PG/PC Interface, choose CP5611(PROFIBUS) as the access point of the application COMProfibus.
4. Open SIMATIC NET Diagnostics, select the CP5611, and verify:
   • Firmware version is visible
   • Bus status shows Online when connected to an active bus
   • Node address is set (default 0; for point-to-point service cable set to 0 or 1 depending on TDC rack)
5. If the CP5611 is used in diagnostic mode (read-only), set PG is the only master on the bus in the access point properties to avoid bus parameter conflicts with the CP50M0 acting as DP master.

7. COMProfibus V5.1 on Windows 7 Compatibility

COMProfibus V5.1 was developed before Windows 7 existed and is not officially certified by Siemens for that operating system. Field experience shows mixed results:

For long-term reliability on a Windows 7 PG, install COMProfibus V5.1 inside a virtualized Windows XP environment (VMware, VirtualBox) and present the CP5611 as a passthrough or use a USB-to-PROFIBUS adapter (CP5711) bridged into the VM. The native Windows 7 path is workable for occasional parameter downloads but should not be used for factory acceptance tests.

8. Cable Connection: CP5611 to TDC Rack

The service cable referenced in the TDC Hardware Manual is not a stock PROFIBUS cable. It carries the DP signals plus the parameterization handshake on a separate pin pair that the CP50M0 exposes for engineering access. The cable must be ordered as a spare part from Siemens; field-built substitutes risk damaging the parameterization port.

9. Modernization Path: Migrating to TIA Portal

For new TIA Portal-based controllers (S7-1200, S7-1500, ET 200SP) that need to communicate with the existing CP50M0 / TDC bus segment, the CP50M0 remains the PROFIBUS DP master. The S7-1200 / S7-1500 stations are configured as DP slaves and integrated as PROFIBUS devices in the TIA Portal project. See the official Siemens configuration guide:

• Configuring PROFIBUS DP (S7-1200) - STEP 7 / TIA Portal V20 documentation

When a TDC rack is being decommissioned in favor of an S7-1500 + PROFIBUS master, the workflow is:

1. Read the existing COMProfibus project, or rebuild from the wiring documentation.
2. Create a TIA Portal project, add the S7-1500 CPU and the CP 1542SP-1 / CM 1542-1 PROFIBUS master module.
3. Insert each DP slave from the GSD library using the same addresses as the legacy CP50M0 configuration.
4. Map the cyclic I/O to the S7-1500 process image; mirror the data-block offsets used by the TDC application.
5. Perform a side-by-side cutover with the COMProfibus project archived for fallback.

Conversely, if the S7-1200 / S7-1500 is the DP master and the TDC remains as a slave station, it is rarely practical: the CP50M0 firmware does not expose a DP slave mode. Migration scenarios therefore favor replacing the CP50M0 + TDC with a SIMOTION or S7-1500 + CP 1542 combination.

10. Diagnostic Reading and Troubleshooting

Live diagnostic data from a DP slave can be read from a STEP 7 / TIA Portal CPU using the DPNRM_DG instruction (read diagnostic data from a PROFIBUS DP slave). The function returns the standardized diagnostic buffer defined by EN 50 170 Volume 2, which includes station status, manufacturer-specific diagnostic bytes, and module status. Reference: DPNRM_DG instruction - S7-1200 manual collection, TIA Portal V20.

Although DPNRM_DG runs on an S7-1200 / S7-1500, the same diagnostic frame structure is broadcast by the CP50M0 on the bus and can be captured by COMProfibus online diagnostics:

1. In COMProfibus, choose Online → DP Diagnostics.
2. The tool polls every active slave and displays station status byte 1 and 2.
3. For extended manufacturer-specific diagnostics, double-click the affected slave — COMProfibus parses the GSD-declared diagnostic blocks.

CP50M0 LED state decoding

11. Verification, Commissioning, and Acceptance Test

After a successful Export-DP Master, execute the following acceptance sequence before handing the TDC rack back to operations.

1. Power-cycle the CP50M0 to confirm the project survives a cold restart.
2. Compare the cyclic I/O image in the TDC application against the COMProfibus project — every configured slot must show the expected byte count.
3. Disconnect one slave and verify the BF LED changes state within one bus cycle (T_TR).
4. Reconnect the slave and confirm automatic recovery without operator action.
5. Capture the COMProfibus online diagnostic buffer and archive it in the project folder acceptance/<date>/.
6. Update the wiring diagram revision number and store the new .pdb in the same folder, renamed with the date.

Troubleshooting Matrix

Frequently Asked Questions