Configuring Profibus DP Between S5-135U IM308C and MP277 HMI

Overview

This article documents the procedure for establishing a Profibus DP link between a legacy SIMATIC S5-135U programmable controller (CPU 928 in this case) equipped with an IM 308-C DP master interface, and a SIMATIC MP 277 Multi Panel HMI acting as a DP slave. The workflow described here was originally validated against an S5-135U/928 chassis fitted with a 6ES5 308-3UC11 IM 308-C, with the master configuration stored on a 5.25" CF card produced by COM Profibus V5.1 and the HMI project built in WinCC flexible.

The integration is non-trivial because the S5/IM 308-C platform was designed for a generation in which Profibus nodes had to be selected from GSD catalogs rather than imported from newer TIA hardware catalogs. The MP 277 belongs to a later generation and its GSD was not always shipped in the historical COM Profibus V5.x distribution, which is why most searches terminate at the older MP 270 / MP 270B types.

Engineers migrating from ProTool to WinCC flexible on a MP 270 fleet, or replacing an obsolete MP 270 by a MP 277, can reuse the existing master configuration file only after substituting the MP 270 GSD by the MP 277 GSD and recompiling the bus parameters in COM Profibus.

Hardware and Software Components

The IM 308-C interface module is documented in the official PI (PROFIBUS & PROFINET International) product finder entry for Interface IM 308-C. It connects the SIMATIC S5-115U/H, S5-135U and S5-155U/H families to a Profibus-DP segment and supports both master and slave roles depending on the firmware variant loaded.

Profibus DP Architecture in This Stack

The classical S5 + MP 277 topology is a DP-V0 broadcast segment where the IM 308-C acts as class 1 master and the MP 277 acts as a DP-V0 slave. Communication uses cyclic I/O data exchange with a fixed, project-planned slot allocation that is mirrored on the WinCC flexible side through the "SIMATIC S5 DP" channel.

From an addressing standpoint:

• The S5 user program reads/writes its I/O area in the CPU process image.
• The IM 308-C reads the DP output image on the backplane bus and broadcasts it to the slaves.
• The MP 277 receives its inputs from the master and exposes the configured byte/word area in the panel's tag database.
• Operator events (button states, value entries) are sent back as DP inputs the master will see.

Why a GSD File Is Required

Each Profibus DP slave on a segment is described to the master configuration tool by a Device Master File (GSD). The GSD tells COM Profibus:

• The device's vendor and product identifiers (Ident_Number).
• Supported baud rates and bus timing.
• Modular slot layout (number and sizes of input/output slots).
• Optional diagnostics, sync/freeze capability, and fail-safe behavior.

Without a matching GSD for the MP 277, COM Profibus V5.1 cannot resolve a slave type for the panel and the configuration cannot be flashed to the IM 308-C. This is also why the "SIMATIC S5 DP" driver inside WinCC flexible can be opened (it is a generic DP slave profile) but the bus cannot be brought up: the master configuration is incomplete.

Locating the MP 277 GSD File

The MP 277 shipped with a vendor-specific GSD that was historically distributed through Siemens customer support and the Siemens Industry Online Support portal, not through the official COM Profibus V5.x install media. The modern path is the SIOS GSD download entry; the canonical MP 277 GSD can be requested or downloaded through entry ID 29339779 in Siemens Industry Online Support article 29339779 - GSD files for SIMATIC HMI panels.

Search procedure if the direct entry is no longer accessible:

1. Open the SIOS support portal and search for "GSD MP 277" or "GSD SIMATIC HMI panels".
2. Filter by "Downloads" and select "GSD" as content type.
3. Confirm the file is the binary/PNO GSD (typically named SIEM8167.gsd or similar, with the vendor ID 0x802A and Ident_Number for the MP 277 family).
4. If you cannot find a public download, request the GSD through your regional Siemens technical support channel; many automated systems expose a "Siemens hotline" distribution path for HMI GSDs that were not added to the COM Profibus install bundle.

Prerequisites

• PC with COM Profibus V5.1 + service pack (or later minor version) installed.
• PC with WinCC flexible 2008 or later (SP level compatible with the MP 277 image).
• MP 277 GSD file (downloaded from SIOS or supplied by Siemens support).
• Step 5 project for the S5-135U (if you intend to integrate the IM 308-C init blocks FB 192 / FB 193 / FB 194 / FB 230 / FB 255 from the COM 308-C package).
• PG/PC cable or MPI/Profibus adapter for flashing the IM 308-C CF card and for commissioning.
• Profibus cable, Profibus connectors with terminating resistors activated only at segment ends.

Step-by-Step: Building the DP Master Configuration

Step 1 - Install the MP 277 GSD

Open COM Profibus V5.1, then in the project tree choose Extras > Install GSD and point to the directory holding the .gsd file. After installation, the MP 277 will appear in the DP slave catalog under the manufacturer "Siemens AG" / "SIMATIC HMI" or under the directory configured by the GSD's vendor block.

Step 2 - Create or open the master project

Create a new DP master project and select "IM 308-C" as the master type. In the master parameters, set:

Step 3 - Insert the MP 277 as a slave

Drag the MP 277 from the slave catalog to the segment. Assign a Profibus address that does not conflict with any other slave on the segment (the IM 308-C reserves address 0 for itself unless reconfigured). The default factory address for the MP 277 is typically 1 or 2; verify in the Control Panel > Settings > Profibus DP dialog of the panel.

Step 4 - Configure cyclic I/O slots

Open the slot configuration of the MP 277. The MP 277 family typically exposes one input slot and one output slot, each 8 bytes by default in the standard GSD. Map the slots to the byte addresses used inside the S5 user program.

Example mapping (cyclic DP-V0 / 8 bytes in / 8 bytes out):

MP 277 Slot 0 - Output   = S5 PIB/PQW 0..7
MP 277 Slot 0 - Input    = S5 PEB/PIW 0..7

These exact addresses will be referenced by WinCC flexible under the "SIMATIC S5 DP" channel as the panel tag area.

Step 5 - Validate and save

Run the COM Profibus "Check" function. Errors must be resolved before exporting - typical failures are "Ident_Number mismatch" (wrong GSD installed), "Slot 0 not assigned", or "Baud rate not supported by slave". When validation passes, save the project as a *.cbs / *.dat file ready for export to the flash card.

Step-by-Step: Exporting the Master Image to the IM 308-C CF Card

1. Connect the CF writer to the PC and insert the SRAM/flash card.
2. In COM Profibus, choose File > Export > CF/Flash card.
3. Select the IM 308-C target (firmware image matters - older IM 308-C cards require a "flush" mode, the -3UC2x variants accept a direct export).
4. Wait for the green status LED / "Write successful" dialog.
5. Eject the card. Insert it into the IM 308-C module with the PLC de-energized.

Step-by-Step: WinCC Flexible Side on the MP 277

1. Create / open the MP 277 project in WinCC flexible.
2. Open Project > Connections and add a new connection with driver "SIMATIC S5 DP".
3. On the connection's parameters, set the PLC type to a SIMATIC S5 928 / 938 compatible profile and the Profibus address to the same address used in COM Profibus (must match the physical panel setting).
4. Define tags whose addresses are within the byte range configured in the master's slot 0 (e.g., DB or bit/byte area pointer). For "SIMATIC S5 DP" this is typically a flag/byte area pointer using the area "P" / flag byte.
5. Compile the project and transfer it to the panel using RS-232, USB-PPI bridge, MPI, or Ethernet (depending on panel variant).

Sample S5 Function Block Integration

The IM 308-C is initialized from the S5 user program through standard DP init blocks. With a single MP 277 slave, the call is straightforward:

// FB 192 - DP_INIT: initialize IM 308-C
// FB 193 - DP_CALC_IO: calculate I/O addresses
// FB 230 - DP_SEND  : send process data
// FB 255 - DP_RECV  : receive process data
//
// In OB1 / OB251 call:
// CALL  FB192, DB192     // init, slots defined in COM Profibus
//   SSNR  := KY 0,0      // interface number
//   ADRM  := ...         // slave diagnostic address
// CALL  FB255, DB255     // receive input process image from MP 277
//   SSNR  := KY 0,0
//   ADEP  := KF 0
//   RET   := MW 100
//   ...
//

The exact structure depends on the COM 308-C block library in use and the slot ordering in COM Profibus; refer to the COM 308-C block help for the parameter list your STEP 5 project owns.

Verification

After loading, perform the following checks with the rack energized and the panel connected:

1. IM 308-C LEDs: All expected front-panel indicators normal: +5 V, BF (bus fault) off, SF (station fault) off, RUN on. BF/SF on indicates a parameterization failure.
2. MP 277 Profibus diagnostics screen: Control Panel > Diagnostics > Profibus DP. The MP 277 must report "Active, no diagnostics, data exchange OK".
3. COM Profibus online view: Reconnect COM Profibus online via MPI/Profibus and confirm the slave is in "Data Exchange" state (state 8) and I/O is swapping cyclically.
4. HMI tag test: Set a bit in the S5 user program that is wired to an indicator on the panel. The visual state must update without manual refresh, within the typical DP-V0 cycle time of 1 to 10 ms at 1.5 Mbit/s.
5. Reverse test: From a button configured in WinCC flexible, toggle a flag in the S5 area the user program monitors. CPU must see the bit flip within one bus cycle.

Troubleshooting Matrix

Operating the S5 as a Slave on a Mixed Bus

If you later add an S7-300/400 master (or other DP-V0 class 1 master) on the same segment with the S5 as a slave, the procedure is documented in Siemens support entry 6556876 - Operating an S5 with IM 308-C as a DP slave. The article walks through installing the S5 "IM308-C DP-Slave" entry in the master's catalog and assigning the slots the same way as in the master-master case.

Migration Notes: MP 270 to MP 277

Engineers migrating from MP 270 / MP 270B (now obsolete) to MP 277 should consider these points:

• The GSD files are not interchangeable. The MP 270 GSD cannot be reused as a placeholder on the MP 277. The Ident_Number differs and the slot sizing may also differ.
• The WinCC flexible project transfers reasonably well via the ProTool → WinCC flexible migration path, but the Profibus connection must be re-added because the area pointer schemes are not identical between ProTool and WinCC flexible on this product pair.
• Flash card contents must be regenerated if the address area changes during migration. Do not assume that an existing CF card for the previous MP 270 will work with the new panel on the same address.

Frequently Asked Questions