Interfacing Third-Party Endress+Hauser PROFIBUS PA Instruments Behind AFDiSD Couplers: SITRANS Library vs Standard APL Drivers

In SIMATIC PCS 7 V8.2 architectures utilizing AFDiSD (Active Field Distributor with Diagnostics) on PROFIBUS PA segments, third-party field instruments—such as Endress+Hauser Promag flowmeters, Cerabar pressure transmitters, or Micropilot radar level gauges—CANNOT use the Siemens SITRANS Library. The SITRANS Library is strictly proprietary to Siemens field hardware and will reject non-Siemens devices with permanent device mismatch errors (QWRONDEV). To interface Endress+Hauser and other third-party PROFIBUS PA instruments cleanly behind AFDiSD couplers (especially in fault-tolerant CPU 410-5H redundant systems), engineers must use standard PCS 7 APL channel blocks: Pcs7AnIn (or standard FbAnIn) for analog measurement inputs, Pcs7DiIn for discrete switches, and Pcs7AnOu for valve positioners.

Architecture of AFDiSD Active Field Distributors on PROFIBUS PA

In modern process automation architectures, hazardous field environments (Zone 1 / Zone 2 / Division 2) interface with DCS controllers via PROFIBUS PA segments connected through AFDiSD (Active Field Distributor with advanced Sub-segment Diagnostics 6ES7157-0AC85-0XA0 or 6ES7655-5DX00-1BB0).

The AFDiSD provides galvanic isolation, short-circuit containment per spur line, automated segment termination, and continuous physical-layer supervision (measuring bus voltage, signal jitter, noise levels, and wire breaks). It transparently passes standard PROFIBUS PA telegrams conforming to the international IEC 61158-2 and PROFIBUS PA Profile 3.0 standards, regardless of whether the connected transmitter was manufactured by Siemens, Endress+Hauser, ABB, or Emerson.

Why the SITRANS Library Rejects Third-Party Field Instruments

Engineers frequently ask whether they can utilize the advanced faceplates of the SITRANS Library for third-party instruments. The answer is an absolute NO:

Embedded Firmware Handshake: SITRANS function blocks (e.g., MAG6K, SITR_TH) execute proprietary acyclic DPV1 read requests (RDREC) querying manufacturer-specific slots for Siemens-specific identification signatures.
The QWRONDEV Lockout: When an Endress+Hauser transmitter responds with its official PNO Manufacturer ID (0x0011) rather than Siemens (0x002A), the SITRANS block immediately asserts QWRONDEV = 1 ('Wrong Device Connected') and disables all process value outputs.
Redundant CPU 410 Driver Clashes: Furthermore, installing the SITRANS Library driver installer on an Engineering Station can overwrite standard driver generation XML templates, corrupting FbAnIn module driver generation across redundant S7-400H / CPU 410-5H controllers.

Engineering Standard APL Channel Drivers: Pcs7AnIn and FbAnIn

To interface Endress+Hauser PROFIBUS PA devices seamlessly in PCS 7:

HW Config Device Integration: In Step 7 HW Config, insert the Endress+Hauser instrument under the DP/PA Link or Coupler using either the official manufacturer GSD file or the standardized PA Profile 3.0 GSD (e.g., PA139700.GSD for 1-channel analog input transmitters).
Assign Symbolic Process Image: Assign the 5-byte input address (4 bytes IEEE 754 REAL process value + 1 byte Quality Code) to a symbolic tag (e.g., FT_101_PV).
CFC Block Selection:
- Pcs7AnIn (FB1869): The standard APL analog input driver. Connect PV_In symbolically to FT_101_PV. The driver automatically decodes the floating-point measurement and passes the PA Profile status byte into the APL structure tag (.Value and .ST).
- FbAnIn (FB1813): The specialized fieldbus analog channel block, used when detailed diagnostic interconnectivity to PA Link diagnostic blocks is required.

Module Driver Generation in Redundant CPU 410-5H Systems

When compiling CFC charts in a redundant CPU 410-5H environment:

Enable Generate module drivers during CFC compilation.
The PCS 7 driver generator detects the DP/PA Link (IM 153-2) and the AFDiSD topology. It automatically generates the diagnostic @ system charts containing DPPA_LNK, MOD_PA, and OB_BEGIN blocks.
If a field wire to an Endress+Hauser device shorts out, the AFDiSD isolates the faulty spur, while the Pcs7AnIn channel block receives quality code 0x00 (Bad), immediately generating a channel fault alarm on the OS without bringing down the rest of the PA bus segment.

Comparison of Fieldbus Integration Options for Third-Party PA Devices

The following table compares driver methodologies for third-party PROFIBUS PA instruments in SIMATIC PCS 7:

Integration MethodologyThird-Party Device SupportRedundant CPU 410-5H SupportAcyclic Diagnostic FaceplatesProcess Value ReliabilityStandard PCS 7 APL (Pcs7AnIn)100% Compatible (Universal)100% Certified and SeamlessStandard APL FaceplatesHighest (Deterministic Cyclic Image)Fieldbus Channel Block (FbAnIn)100% Compatible (PA Profile 3.0)Fully Supported via DPPA_LNKStandard Fieldbus DiagnosticsHighest (Full PA Status Byte Decoding)Siemens SITRANS Library0% (Incompatible / Blocks Third-Party)Severe limitations with PA positionersDetailed Siemens-only screensBlocked by QWRONDEV ErrorSIMATIC PDM (Engineering View)100% Compatible (via Vendor EDD)Non-intrusive Acyclic RoutingDeep calibration and health logsN/A (Acyclic Parameterization Tool)

Verification

Verify third-party PA instrument communication behind AFDiSD:
1. Inspect the AFDiSD physical LEDs: verify that the spur LED connected to the Endress+Hauser transmitter is solid green (indicating normal bus voltage and impedance).
2. Open the CFC chart online in Test Mode; confirm that Pcs7AnIn (or FbAnIn) displays the live measured process value (PV_Out.Value) matching the field transmitter display.
3. Verify that the output status byte (PV_Out.ST) indicates 16#80 (Good).
4. In SIMATIC PDM, execute a communication test; confirm that the Endress+Hauser vendor EDD loads and allows parameter reading over the bus.

Limitations and Operational Precautions

Never attempt to modify SITRANS block code to bypass QWRONDEV checks; the internal algorithms are know-how protected and altering them voids technical support. When mixing instruments from multiple manufacturers on a single PA segment behind AFDiSD couplers, ensure the total current consumption of all devices plus the 30 mA reserve does not exceed the maximum current rating of the DP/PA coupler (typically 1000 mA for Ex [ia] couplers).

Engineer FAQ

Can I use SIMATIC PDM to calibrate Endress+Hauser devices even if I use APL blocks?

Yes. SIMATIC PDM communicates acyclically using vendor-supplied EDD device descriptions, completely independent of the cyclic APL runtime blocks executing in the AS controller.

Why did my FbAnIn driver connections disappear after installing SITRANS Library V6?

Early versions of the SITRANS Library V6 installer had a known bug where it overwrote standard PCS 7 driver generator XML definition files. Re-running the PCS 7 system update or repairing the PCS 7 Basis Library restores proper driver generation.

What GSD file should I use for an Endress+Hauser PA transmitter in HW Config?

You can use either the specific Endress+Hauser GSD file provided on the manufacturer's website or the standardized Siemens/PI generic Profile GSD file (e.g., PA139700.GSD for standard 1-channel analog inputs).