Resolving Siemens CP5711 Error 33:17075 on S7-300 MPI/PROFIBUS

1. Problem Overview

The Siemens CP5711 (catalog 6GK1571-1AA00) is a USB-attached MPI/PROFIBUS communications processor used to connect engineering workstations (PG/PC) to SIMATIC S7-300, S7-400, and C7 controllers. When the workstation runs STEP 7 (SIMATIC Manager) or SIMATIC NET and attempts to go online with an S7-300 CPU whose PROFIBUS segment already carries a DP device (for example an ET200 remote I/O station, a SINAMICS G120 inverter, or a TP/OP HMI), the engineering station often reports internal error 33:17075. The same fault surfaces inside SIMATIC NET Diagnostics as hex code 0x0313 with the message "LogDevice is not active! Blink-Test failed!".

The fault is reproducible only when an additional DP device is present on the segment: a direct male-male cable (6ES7901-0BF00-0AA0) between the CP5711 and the CPU MPI/DP socket works every time. The condition is independent of the bus baud rate and of the CPU firmware revision, but it correlates strongly with IRQ/address assignment on the PG, with the PG/PC interface profile selected inside STEP 7, and with the way the PROFIBUS segment is terminated.

This article consolidates the diagnostic flow from Siemens KB 11492532 - Diagnostics and Remedy in STEP 7, the STEP 7 V5.x readme (section 4.4.1), the CP5711 product support page, and the SIMATIC NET commissioning manual. It is intended for service engineers who must restore the online connection without replacing hardware.

2. Affected Hardware, Software, and LED Code Reference

The fault is independent of the DP slave vendor; it has been reproduced with Siemens ET200S, ET200M, SINAMICS G110/G120, SINAMICS V20, and TP177B panels.

2.1 CP5711 LED status reference

The pattern that prefigures error 33:17075 is "ACTIVE blinking red at 2 Hz while ERR stays dark" - this is the visual fingerprint of an IRQ conflict that loses frames only when the bus carries traffic.

3. Diagnostic Symptoms and Error Code Mapping

The fault surfaces in three independent layers. Every layer must be cleared before the next one is investigated; a partial fix leaves the segment unusable.

3.1 STEP 7 / SIMATIC Manager symptom

Selecting PLC → Accessible Nodes, or pressing the Online button in HW Config, returns the internal dialog:

Error 33 : 17075
Cannot establish a connection to the target module.
The access point S7ONLINE is set to interface CP5711.MPI.
Refer to the entry in the log file %TEMP%\s7logs\s7log.txt

The numeric pair 33:17075 is the S7API error code. The high word (33) maps to S7ONLINE_NO_CONNECTION; the low word (17075 = 0x42B3) maps to S7_TRANSPORT_TIMEOUT. STEP 7 catches the underlying PROFIBUS error and remaps it to this generic user-visible pair.

3.2 SIMATIC NET Diagnostics symptom

Launch Start → SIMATIC → SIMATIC NET → Diagnostics, select the access point CP5711.MPI, and press Test. The dialog returns:

0x0313 - Initialization failed
LogDevice is not active!
Blink-Test failed!

Hex 0x0313 is the internal SIMATIC NET return code for "device-open failed because the bus is not in operational state". The blink test is a hardware-level test that flashes the CP5711 LEDs to confirm USB enumeration. Failure here proves the driver could not initialise the CP firmware against the live segment, although the same CP passes the test against a one-to-one CPU-only link.

3.3 Topology-dependent behaviour

• Direct male-male cable (6ES7901-0BF00-0AA0) from CP5711 to CPU MPI/DP socket → online OK, blink test OK.
• Same cable plus a DP device on the segment → online fails with 33:17075.
• A second PG with identical PG/PC interface settings connects successfully through the same segment → cabling, termination, and bus profile are not the root cause.

This pattern is the fingerprint of an IRQ or resource conflict, not of a bus fault.

3.4 Related error codes that share the same root cause

4. Root Cause Analysis

Field analysis consistently points to one of three classes of defect. The diagnostic procedure in Section 9 addresses them in the order of statistical likelihood.

4.1 Interrupt / address assignment conflict

The STEP 7 V5.x readme (section 4.4.1, "Integrated MPI on-board and the MPI PC module") documents a known incompatibility between the CP5711 driver and other USB or PCI devices that share the same IRQ or memory I/O window. On Windows 7 and Windows 10 the CP5711 enumerates as a USB Human Interface Device and a virtual network adapter; both require a contiguous block of memory below 4 GB. When the CPU has DP slaves active, the host controller sees additional token rotation frames; if an IRQ line is shared, the CP5711 driver loses frames and reports 0x0313. The fault does not appear in the direct CPU-only link because no token rotation is needed.

Reference: Siemens KB 11492532, sub-procedure "Check the interrupt and address assignments".

4.2 PG/PC interface profile mismatch

The access point CP5711.MPI carries a bus profile, a baud rate, an HSA, and a station address. Mismatches that trigger 33:17075 include:

• Baud rate set to 1.5 Mbps while the segment runs at 187.5 kbps (or vice-versa).
• HSA (highest station address) lower than the highest DP slave address on the segment.
• Bus profile set to Standard instead of DP (Universal) when the segment carries DP-V0 slaves.
• PG address colliding with an active node (the CPU default address is 2; the PG default is 0 or 1).

The Standard profile, used historically for MPI-only networks, limits token rotation; an ET200 or SINAMICS increases traffic and the CP5711 drops out of the ring.

4.3 PROFIBUS termination and shielding

Although termination does not affect the direct CP5711-to-CPU link, it is the dominant cause of the same error when multiple devices share the segment. The PROFIBUS standard (IEC 61158-2 / IEC 61784) requires exactly two terminators at the physical ends of the segment, implemented as 220 Ω between lines A and B plus 390 Ω pull-ups to VP and pull-downs to GND. Mid-segment terminators produce reflections that the CP5711 decodes as framing errors.

On Siemens 6ES7972-0BA12-0XA0 connectors the terminator is engaged by sliding the orange switch toward the cable gland. A loose switch is the single most common field defect.

5. Interrupt and Address Configuration

Follow the Siemens procedure from KB 11492532 step by step.

1. Open Windows Device Manager (devmgmt.msc).
2. Expand Network adapters and locate SIEMENS CP5711.
3. Right-click → Properties → Resources tab. The Interrupt request line shows the IRQ number.
4. Open Start → Run → msinfo32. Confirm that no other active device shares the same IRQ.
5. If a conflict exists, disable or re-seat the conflicting device, then unplug the CP5711 and re-plug it into a different USB root hub. On desktop towers prefer the rear ports; avoid USB hubs in the chain because they introduce extra latency that the CP5711 cannot tolerate at 12 Mbps.
6. Re-check the IRQ and the memory I/O range. The CP5711 requires an I/O window in low memory (typically 0xD000-0xD7FF); a value above 0xE0000000 is incompatible with the legacy S7API stack in STEP 7 V5.5.
7. If the IRQ keeps shifting after each reboot, open BIOS → Advanced → PCI Subsystem Settings and disable IRQ rebalancing. Re-enable it only on managed laptops where suspend/resume must preserve IRQs.

6. PG/PC Interface Settings Reference

If Automatic bus profile detection is enabled but the CP5711 cannot read the live list (because of an IRQ conflict), the dialog silently falls back to Standard and the next online attempt fails with 33:17075. The fallback is logged in %TEMP%\s7logs\s7log.txt with severity Warning.

6.1 Diagnostic flow

7. PROFIBUS Topology, Termination, and Token Rotation Timing

A correct PROFIBUS segment is a single linear bus with exactly two terminators at the physical ends. No stubs longer than the maximum stub length for the chosen baud rate are permitted.

If the CP5711 sits mid-segment, both its onboard terminator (when present on the DP connector) and any far-end terminator must be OFF; only the two physical ends of the segment (CPU and last DP device) carry the 220 Ω termination. For multi-device segments the maximum segment length at each baud rate is:

PROFIBUS uses RS-485 signalling: differential voltage ≥ 1.5 V across 50 Ω, common-mode range -7 V to +12 V. Shielded twisted pair (Siemens 6XV1830-0EH10 violet cable, 150 Ω nominal impedance) is required; UTP cable is not compliant.

7.1 Token rotation timing

The PROFIBUS token rotation time (TTR) is calculated from the configured HSA and the slot time (Tslot). For a stable segment with a CP5711 acting as Class 1 master:

TTR_target  = max(1 ms, 10 ms * HSA / 32)
Tslot       = max(11 * Tbit, 38 * Tbit + 2 * Tprop)
Tbit        = 1 / baud_rate

At 1.5 Mbps, Tbit = 667 ns. With 10 stations and Tprop = 1 µs, Tslot ≈ 50 µs, TTR_target = 3.1 ms. The CP5711 issues a token every TTR window; an IRQ-stalled driver that misses one slot reports 0x0313 after the second consecutive loss.

8. CP5711 Driver and Firmware Verification

The CP5711 firmware is bundled with SIMATIC NET, not with STEP 7 alone. After a fresh STEP 7 re-install the firmware may revert to an older revision that mis-handles multi-master segments. The Siemens recommended sequence is:

1. Uninstall STEP 7 / SIMATIC Manager through Control Panel → Programs and Features.
2. Uninstall SIMATIC NET completely (Start → SIMATIC → SIMATIC NET → Commissioning → Remove).
3. Reboot. Remove residual CP5711 drivers manually:

   del C:\Windows\System32\drivers\siavxx.sys
   del C:\Windows\System32\s7onlinx.dll
   reg delete "HKLM\SOFTWARE\Siemens\AUTSW\SIMATIC NET" /f

4. Re-install SIMATIC NET first, then STEP 7, in that order. This sequence registers the S7API hooks in the correct order.
5. Update CP5711 firmware through Start → SIMATIC → SIMATIC NET → Set PG/PC Interface → CP5711 → Firmware Update. Target firmware ≥ V2.0.0.0; older V1.x firmware mis-handles DPV1 retries.
6. Verify the digital signature on siavxx.sys through Properties → Digital Signatures. The signer must be Siemens AG; unsigned drivers will load under Windows 10 only if test signing is enabled.
7. Reboot and re-run the diagnostics test.

9. Step-by-Step Resolution Procedure

Execute the steps in order. Do not skip the verification after each block; a partial fix masks the next fault.

1. Confirm bus parameters: open HW Config, double-click the CPU MPI/DP interface, and note the baud rate and HSA. Repeat for every DP slave in the live list.
2. Open Set PG/PC Interface. Select CP5711.MPI(Active). Press Properties. Match baud rate, HSA, and bus profile to the values from step 1.
3. Press Diagnostics inside the same dialog. Verify that the live node list contains the CPU and all slaves. A red node indicates a wiring or addressing fault independent of the CP5711.
4. Inspect the IRQ in Windows Device Manager as described in Section 5. Re-seat the CP5711 to a different USB port if any conflict is detected.
5. Power down the plant. Verify that exactly two terminators are engaged: one at the CPU connector and one at the last DP device. All mid-segment connectors must have terminators OFF.
6. Measure the bus with an oscilloscope on a non-terminated stub. Healthy differential swing is 2.5 V peak; below 1.0 V the segment is mis-terminated or cable-broken.
7. Reboot the PG. Run SIMATIC NET Diagnostics → Test. The blink-test must succeed and the live list must show all expected nodes.
8. From STEP 7, run PLC → Accessible Nodes. The CPU must appear within 5 s without error 33:17075.
9. If the error persists, capture the STEP 7 log (%TEMP%\s7logs\s7log.txt) and the Windows event log (eventvwr.msc → Application → S7ONLINE) and contact Siemens Technical Support through the official support channel with the bundle.

9.1 Alternate PC adapter cross-check

10. Verification Tests

After the corrective action, run the four checks below before declaring the segment healthy.

If any check fails, return to Section 9 and re-run from step 1. Do not patch the symptom in isolation; each test depends on the previous one.

11. Preventive Best Practices and TIA Portal Migration Notes

• Lock the CP5711 firmware revision in the engineering workstation image. An uncontrolled Windows update can re-install an older S7ONLINE stack and re-introduce 33:17075.
• Document the PG/PC interface configuration in the project README. Every engineering station that touches a live segment must use identical bus profile, baud rate, and HSA.
• Maintain a stock of 6ES7972-0BA12-0XA0 connectors with switchable terminators. Field failures are often a slipped switch rather than a software fault.
• For large plants, prefer a dedicated PROFIBUS diagnostics tool (e.g., Softing PROFIBUS Diagnostic Tool, Indu-Sol PROFINET-INspektor) to capture bus traces that the CP5711 alone cannot.
• Schedule an annual bus health check using the Siemens PROFIBUS Diagnostics feature in HW Config. The function reads the live list, the repeat-counter, and the lost-token count, and reports drift before it becomes an outage.
• When migrating a STEP 7 V5.5 project to TIA Portal, reuse the CP5711 access point but create a new S7ONLINE entry pointing to CP5711.PROFIBUS.1; the legacy CP5711.MPI access point is reserved for MPI-only projects and will fail when DPV1 slaves are present.
• Use a USB port on the rear I/O panel of a desktop tower for commissioning. Front-panel headers and external hubs introduce extra polling latency that can push the CP5711 over its 1 ms token budget.
• Disable Windows Defender real-time scanning on the STEP 7 install directory and the SIMATIC NET service folders; on first boot the AV can hold a file handle long enough that the S7API initialisation times out and surfaces as 33:17075.

FAQ