Resolving STEP 7 V5.4 SP2 MPI Upload Failure on SINUMERIK 810D

Problem Overview

The classic failure mode reported in field service is asymmetric port behavior on a SINUMERIK 810D: STEP 7 V5.4 SP2 uploads succeed on the Profibus port but fail on the MPI port with a generic "OUpload" or online communication error. The PLC is reachable on one physical channel and unreachable on the other, which typically rules out a cable, terminator, or 24 V supply problem and points to PG/PC interface configuration, slot addressing, and bus profile settings on the engineering station.

This article consolidates the diagnostic path that resolves the issue: confirming node visibility through Accessible Nodes, isolating the PG/PC interface assignment, validating the baud rate via Automatic Bus Profile Detection, and forcing the correct slot number 2 for the 810D PLC CPU when the project was not loaded to the PG. The procedure applies to STEP 7 V5.4 SP2 and later service packs in the V5.4 line, and to SINUMERIK 810D with integrated S7-300-style PLC subsystem.

SINUMERIK 810D Communication Architecture

The 810D couples an HMI (PCU 50 / PCU 70) and an NCK to a SIMATIC S7-300 PLC core. Three logical buses meet at the 810D operator panel and the integrated PLC:

• MPI bus — Default 187.5 kbps (auto-detect up to 12 Mbps on newer PG adapters). Default station address of the integrated PLC is 2 unless reconfigured.
• Profibus DP — Used for drives (SIMODRIVE 611), I/O stations, and the NCK link. Typical Profibus address for the integrated PLC is 2 by default.
• RS-232 / IPI interface — Service and HMI backup on some variants.

Both the MPI X1 port and the Profibus X2 port on the 810D are physically present on the backplane. The Profibus port and the MPI port are independent segments; communication success on one does not guarantee success on the other because the bus parameters (baud rate, profile, Ttr, Tslot, min Tsdr, max Tsdr, quiet time, GAP factor, retry limit) and the active PG/PC interface on the engineering station are resolved independently for each adapter selection.

Root Cause Analysis — Why MPI Fails While Profibus Works

When Profibus upload succeeds and MPI upload fails on the same controller, the most probable root causes are:

1. PG/PC interface is pinned to a Profibus CP (e.g. CP5611, CP5512, CP5613) instead of the MPI PC adapter. STEP 7 V5.4 SP2 uses one active interface assignment per session; switching the Accessible Nodes view does not change the underlying S7ONLINE access point.
2. Baud rate mismatch on the MPI segment. The 810D PLC MPI port supports 19.2 kbps and 187.5 kbps by default. If the network has been reconfigured (operator parameter block, PLC hardware config, or an HMI-MPI project download) to 19.2 kbps, the PG running at 187.5 kbps will time out on every request.
3. Wrong slot number in Accessible Nodes. The integrated PLC of the 810D is a virtual slot; the diagnostic reply is only valid if STEP 7 polls the correct slot index. The field-tested slot index is 2. Slot 0 and 3 will return "node not found" even when the bus is healthy.
4. Bus profile / network detection not executed. Without Start Network Detection, STEP 7 V5.4 SP2 cannot resolve the active bus parameters and will silently fall back to the last known profile.
5. MPI terminator missing on a 2-node link. Profibus frequently has built-in termination on the CP or the 810D connector. MPI requires external 220 Ω termination on both ends with bias, which is often forgotten when the cable is re-pulled for a service visit.

Prerequisites

• STEP 7 V5.4 SP2 installed, license for STEP 7 Professional active where required.
• Siemens PC Adapter USB (6ES7 972-0CB20-0XA0) or MPI-USB cable, or CP5611/CP5613 with MPI firmware loaded.
• MPI PROFIBUS cable with 220 Ω termination at both ends (or use the integrated termination of the PC Adapter).
• Default MPI station address of the 810D PLC is 2. The MPI network must have at least the master (PG) and one slave (810D) connected, and at most 32 nodes including repeaters.

Step-by-Step Resolution

Step 1 — Open the PG/PC Interface Dialog

From the Windows desktop of the PG:

1. Launch Start → SIMATIC → STEP 7 → Set PG/PC Interface (or Options → Set PG/PC Interface inside the SIMATIC Manager).
2. Under Interface Parameter Assignment Used, select PC Adapter (Auto). If the cable is a USB PC Adapter, Windows enumerates it as PC Adapter USB. If the cable is RS-232, select PC Adapter (MPI) –> COMx.
3. Click Properties and confirm the MPI tab shows the cable target as PC Adapter, not CP5611 or CP5512. CP cards are Profibus-capable and will silently route Profibus frames even when the application asks for MPI.
4. Click OK to apply.

Step 2 — Trigger Network Detection

1. Open SIMATIC Manager → Options → Set PG/PC Interface and confirm the active access point is S7ONLINE pointing to the PC Adapter (MPI).
2. Open Accessible Nodes from the toolbar (or PLC → Accessible Nodes). STEP 7 broadcasts a passive node-scan.
3. Click PLC → Diagnose Hardware and choose Start Network Detection. This forces STEP 7 V5.4 SP2 to read the live bus profile (baud rate, highest station address, GAP factor).
4. Capture the bus profile and the detected node table. If the 810D appears with the correct MPI address and slot, the link is healthy.

Step 3 — Force the Correct Slot Number

If Accessible Nodes returns no node, or returns a node with the wrong slot index, manually set the slot:

1. In the Accessible Nodes window, right-click the empty result pane and select Set Slot Number.
2. Enter 2. This is the slot used by the integrated S7-300 PLC core inside the 810D. Slot 2 is also the slot STEP 7 expects for the S7-300 CPU when the project is offline and the real rack is not physically present.
3. Click Update (F5). The 810D PLC node should appear with its online diagnostic buffer populated.

Step 4 — Re-attempt Upload

1. With the node visible, select PLC → Upload Station to PG.
2. Choose the target project, the CPU slot (2), and the connection target (MPI, address 2, slot 2, rack 0).
3. Confirm. The block container, system data, and HW Config are uploaded. The MPI side will then behave identically to the Profibus side.

PG/PC Interface Configuration Reference

STEP 7 V5.4 SP2 — Relevant Feature Set

STEP 7 V5.4 SP2 is the engineering tool that ships the PROFINET Topology Editor in the standard install, including a graphical and tabular view and an online view with diagnostic information. For service on a SINUMERIK 810D, only the S7-300 part of STEP 7 V5.4 SP2 is required, but the following capabilities of the SP2 line are useful for adjacent diagnostics:

• External tool launch from HW Config for distributed write-protection activation — supported from V5.4 SP2 onwards, useful when the 810D PLC is re-deployed with operator parameter protection enabled.
• CiR (Configuration in Run) object handling in S7-PLCSIM V5.4 SP2 — allows loading of CiR-modified HW Config to the simulated PLC. Use this offline to validate any HW Config delta before pushing it to the live 810D.
• S7 Distributed Safety V5.4 SP5 Update 2 — applies if the 810D's safety-related PLC blocks are to be edited, and pins the V5.4 SPx tool chain baseline.

Reference documentation:

• What's New in STEP 7, Version 5.4 — SP2 (PDF)
• What's New in STEP 7, Version 5.4 — SP5 (PDF)
• Update 2 for SIMATIC S7 Distributed Safety V5.4 SP5
• Service Pack 2 for S7-PLCSIM V5.4

Diagnostic Flowchart

Verification

Validate the fix with the following checks:

1. Accessible Nodes lists the 810D with the configured MPI station address and slot 2.
2. PLC → Diagnostic / Set Time of Day round-trips within 1 second, confirming a healthy PG ↔ PLC connection.
3. PLC → Upload Station to PG returns the project, the system data, and a complete block container matching the live 810D program.
4. Online → Compare Blocks against the uploaded program shows identical on every block, with no different status indicators.
5. Repeat the same checks from the Profibus side. The MPI side must remain stable after the Profibus cable is unplugged and reconnected, which proves the MPI configuration is independent and self-contained.

Troubleshooting Matrix

Edge Cases and Field-Proven Caveats

• Multiple PC Adapters installed. When more than one PC Adapter (USB) is plugged in, the Windows COM port index can rotate. Lock the COM port in Device Manager → USB Serial Port → Properties → Advanced to a fixed COM number, then re-pin the Set PG/PC Interface entry.
• CP5611 firmware mismatch. A CP5611 loaded with the MPI firmware behaves as an MPI master; a CP5611 loaded with the DP firmware behaves as a Profibus master. The same physical card cannot serve both segments simultaneously. Verify the firmware under Set PG/PC Interface → CP5611 → Properties → MPI / DP tab.
• HMI-MPI is also the MPI master. On a live 810D, the PCU 50 / PCU 70 may hold the MPI token. Run Options → Set PG/PC Interface → Properties and uncheck PG/PC is the Only Master on Bus to allow token sharing. If it stays checked, the HMI may starve the PG and the upload times out at the request phase.
• Slot 2 vs slot 3 in rack 0. STEP 7 V5.4 SP2 always defaults to slot 2 for an S7-300 CPU. The 810D's integrated PLC core is treated as a slot-2 device for online operations. Do not change to slot 3; that is reserved for the IM (interface module) in a real S7-300 rack, not the CPU.
• Service Pack compatibility. The diagnostic path is independent of the service pack level of STEP 7 V5.4. SP2, SP3, SP4, SP5, and SP6 all support the PC Adapter (Auto) interface and the slot-2 access path. Mixed PG and PLC projects from different SP levels can be opened, but the engineering station must match the SP level of the project that was last downloaded to the 810D to avoid silent downgrades.

Commissioning and Safety Notes

Always archive the live 810D program (PG-archived .zip or PLC archive) before any diagnostic upload. STEP 7 V5.4 SP2 supports PLC → Save Service Data, which produces a tamper-evident support package that Siemens support can decode without the original project.

Frequently Asked Questions