Configuring DP/PA Link and Field Instruments in SIMATIC PDM V9.1 via S7-400 Routing

To connect SIMATIC PDM V9.1 to PROFIBUS PA field instruments through a DP/PA Link (IM 153-2 + PA Coupler) via S7-400 routing (PC -> Industrial Ethernet -> CP 443-1 -> CPU 416 -> PROFIBUS DP -> DP/PA Link), two prerequisites are mandatory: a fully compiled and downloaded NetPro routing configuration and proper PG/PC interface assignment. If the Engineering Station cannot see the DP/PA Link, NetPro's system data blocks (SDBs) have not been downloaded to all participating stations (both the PC Station and S7-400 AS), or the PG/PC interface is not set to 'PC internal.local.1'. Once routing tables are loaded, PDM routes EDD diagnostic telegrams transparently across the CPU backplane.

S7 Routing Architecture for SIMATIC PDM Fieldbus Networks

In distributed process automation architectures, smart field instrumentation (pressure transmitters, radar levels, control valves) deployed on PROFIBUS PA networks are engineered and diagnosed centrally using SIMATIC PDM (Process Device Manager). Rather than requiring technicians to connect handheld communicators in the hazardous field area, PDM communicates through multi-hop network routing:

$$\text{Engineering Station} \xrightarrow{\text{Ethernet}} \text{CP 443-1} \xrightarrow{\text{Backplane}} \text{CPU 416} \xrightarrow{\text{PROFIBUS DP}} \text{IM 153-2 (DP/PA Link)} \xrightarrow{\text{Manchester Bus}} \text{PA Field Devices}$$

Because PDM runs on the Engineering Station and does not possess a direct physical connection to PROFIBUS DP or PA, the entire communication chain relies on S7 Routing. The S7-400 CPU functions as a network gateway, unpacking PDM diagnostic packets from Ethernet telegrams and repackaging them into DP/PA master acyclic communication frames (DS 48 / DS 49).

Diagnostic Causes of Communication Failure with DP/PA Link

When PDM V9.1 displays communication errors or fails to discover PA devices, the breakdown typically stems from specific configuration mismatches:

Diagnostic DimensionConfiguration IssueRoot CauseEngineering SolutionPG/PC InterfaceSelected TCP/IP -> Network Card instead of PC internal.local.1Engineering PC bypasses configured PC Station routing tablesSet PG/PC interface to PC internal.local.1NetPro Routing TablesNetPro saved but not downloaded to AS and PCS7-400 CPU lacks routing SDBs mapping Ethernet to DP subnetDownload NetPro configuration to CPU and PC StationDP/PA Link Operating ModeIM 153-2 configured as standard ET 200M slaveDP/PA Link requires special gateway operating mode in HW ConfigConfigure DP/PA Link from PROFIBUS-DP -> DP/PA-Link catalogBaud Rate MismatchDP bus set above supported link speed (e.g., 12 Mbps)Some older DP/PA couplers only support up to 45.45 kbps or 1.5 MbpsVerify maximum DP baud rate supported by IM 153-2

Without downloaded routing tables, the S7-400 CPU treats PDM's incoming routing packets as unroutable frames and drops them silently.

Step-by-Step Configuration Workflow in NetPro and PDM

To establish transparent PDM communication to PROFIBUS PA instruments via S7 routing, execute the following technical procedure:

Configure PC Station in SIMATIC Manager: Ensure your Engineering Station is represented as a SIMATIC PC Station in the project tree, containing an Application and an IE General (or CP 1623) network adapter connected to the Ethernet subnet.
Set PG/PC Interface: Open Windows Control Panel -> Set PG/PC Interface. Set the Access Point of the Application S7ONLINE (STEP 7) to PC internal.local.1. This binds SIMATIC Manager and PDM to the configured PC Station database.
Configure DP/PA Link in HW Config: In HW Config of the CPU 416, navigate to the PROFIBUS DP master line. Insert the DP/PA Link (6ES7153-2BA02-0XB0 or 6ES7153-2BA10-0XB0). Under the link, configure the PA field devices with their assigned PA addresses.
Compile and Download NetPro: Open NetPro. Select Network -> Save and Compile -> Compile All (check routing). Confirm that compilation completes with 0 Errors. Highlight the CPU 416 and select PLC -> Download to Current Project -> Selected Station. Then highlight the PC Station and download its configuration as well.
Synchronize PDM Device Integration Manager (DIM): In SIMATIC PDM Device Integration Manager, verify that the Electronic Device Description (EDD) files for all installed PA devices are imported and integrated into the STEP 7 catalog.
Connect via PDM Process Device View: In SIMATIC Manager, switch to Process Device Network View. Locate the PA instrument under the DP/PA Link, right-click, and select Open Object. PDM establishes live online communication and reads device parameters.

Verification

Confirm that PDM establishes reliable communication with the field instruments through these diagnostic checks:

Device Identification Online: Open the target PA device in SIMATIC PDM. Confirm that the status bar displays Online and that PDM reads the device tag, manufacturer, serial number, and firmware version directly from the instrument.
LifeList Scan Verification: In PDM Network View, right-click the PROFIBUS PA subnet and select Start LifeList. Verify that all physical PA transmitters respond with their configured addresses (e.g., addresses 3 through 125).
Cyclic and Acyclic Coexistence: Verify that the S7-400 AS continues to read cyclic process values (e.g., PV_In on Pcs7AnIn) while PDM simultaneously reads acyclic diagnostic data without causing bus faults or cycle time overruns.

Limitations and Operational Precautions

When configuring DP/PA Links and PDM networks, observe these essential operational precautions:

Coupler Current Capacity: Verify that total current draw of all PA instruments on the bus segment does not exceed the power supply capacity of the PA coupler (typically 400 mA for standard couplers, 110 mA for Ex [ia] intrinsically safe segments).
Address Range Governance: Avoid assigning address 126 to active field devices; address 126 is reserved for uncommissioned factory-default devices awaiting address assignment.
Never Download HW Config in Production Without CiR: Downloading hardware configuration changes to the DP master line will stop PROFIBUS DP communication unless Configuration in RUN (CiR) is strictly configured and utilized.

Engineer FAQ

Why must the PG/PC interface be set to 'PC internal.local.1' instead of my physical network adapter?

Setting the interface to 'PC internal.local.1' routes communication through the Station Configuration Editor and NetPro database. Selecting a physical network adapter bypasses S7 routing tables, preventing multi-hop access across the CPU backplane.

Can PDM communicate with PA devices if the CPU is in STOP mode?

Yes. S7 routing operates at the operating system communication layer. As long as the CPU has power and its hardware configuration is downloaded, routing telegrams pass between Ethernet and PROFIBUS DP even while the AS is in STOP.

What is the difference between DP/PA Link and DP/PA Coupler?

A DP/PA Coupler is a physical layer converter (RS-485 to Manchester Bus) running at fixed 45.45 kbps. A DP/PA Link contains an IM 153-2 module that decouples baud rates, allowing the DP bus to run at high speed (up to 12 Mbps) while translating to PA.