IM151-8 PN/DP Integration via PROFINET I-Device Configuration

1. Problem Statement: Two Parallel IM151-8 PN/DP Filler Systems

Two SIMATIC ET200S filler systems are each controlled by an independent IM151-8 PN/DP CPU module. Each station runs an identical user program: Q0.0 = "Filler_Open", I0.0 = "Filler_Home", and so on. The two stations currently have no PROFINET link between them, no shared SCADA, and no shared symbol table.

The integration requirement is to bring both stations under a single master controller while keeping the physical I/O segments of each filler separate. The two IM151-8 PN/DP heads cannot be merged into one because the second station is being re-purposed as a remote I/O device. The challenge is that, with a single CPU, the byte-by-byte identical peripheral images of the two stations overlap on every digital bit, every analog channel, and every shared flag/DB.

Symptoms encountered without correction:

• Both "filler open" outputs energize simultaneously when either station triggers
• Inputs from Station 2 falsely appear on Station 1's HMI tags
• Data blocks (DB) with the same number but different contents collide
• OB1, OB82 (diagnostic interrupt), OB100 (restart) execute once but reflect only one set of program state
• OB35 / OB40 cyclic and hardware interrupt sources accumulate alarm floods

2. Hardware Identification and Catalog Reference

The integration solution must respect the actual module variants installed in the field. The following order numbers are relevant:

The integration target depends on which IM151-3 variant is on the second station:

• IM151-3 PN (standard, 6ES7151-3AA20-0AB0) — operates only as a PROFINET IO Device. Use Method B or Method C below.
• IM151-3 PN HF (6ES7151-3BA60-0AB0) — supports PROFINET I-Device. Use Method A if both stations must keep a CPU.

Reference: Siemens PROFINET System Description (entry ID 109747175) and the SIMATIC ET200S System Manual.

3. Integration Architecture Comparison

Three architectures resolve the dual-station duplicate-address problem. Each trades complexity against hardware change.

4. PROFINET I-Device Concept (Method A)

An I-Device (intelligent PROFINET device) is a PROFINET node that is simultaneously an IO Device to a higher-level IO Controller and an IO Controller for its own lower-level PROFINET devices. The IM151-8 PN/DP supports I-Device mode from firmware V3.0.3 onward (STEP 7 V5.5 SP2 / TIA Portal V13+).

The I-Device exchanges data with the higher-level controller through one or more transfer areas. Each transfer area is a contiguous byte range in the I-Device's process image that the higher-level controller sees as its own input or output area.

Slot 0 / subslot 1 corresponds to the IM151-8 PN/DP PROFINET interface (the head module). Slot 0 / subslot 2 is reserved for the port interface module. The IO Controller's program references IB 200 exactly as if it were a local input module, but the bytes are physically wired to the second station's peripherals.

5. Method A — Step-by-Step (STEP 7 Classic, SIMATIC Manager)

1. Open HW Config of the I-Device station (the IM151-8 that becomes the subordinate CPU). Right-click the PROFINET interface and select Properties > I-Device.
2. Enable the Operate as I-Device checkbox. The PROFINET device role changes from "IO Device" to "I-Device".
3. Click "Transfer Areas" and add a new area:
   • Type: Input area (data from I-Device to IO Controller)
   • Slot: 0
   • Subslot: 1
   • Start address in I-Device: 100 (decimal)
   • Length: 32 bytes
4. Add the output area with the same length, start address 100, slot 0, subslot 2.
5. Export the I-Device as a GSD file: Station > Export > GSD file. The export will reference the I-Device by its PROFINET device name (assigned in step 6).
6. Assign PROFINET device name: in the I-Device's HW Config, set device name to im151-8-idevice-01 and IP to 192.168.0.20, subnet mask 255.255.255.0, router 192.168.0.250.
7. Import the GSD into the master IM151-8's project: Options > Install GSD. The I-Device appears in the catalog under PROFINET IO > I-Device.
8. Drag the I-Device onto the master's PROFINET subnet. Set the master's view of the transfer area to start at IB 200 / QB 200.
9. Download HW Config to both stations. Use the Assign PROFINET Device Name tool (Accessibility > Target Device) to write the device name to the I-Device's PROFINET interface.

Verification (Method A)

• In the master CPU's online view, force Q200.0. Confirm that the I-Device's Q100.0 follows (visible via online watch on the I-Device CPU).
• Trigger an input on the I-Device (e.g., field-switch closing I0.0 on Station 2). Confirm I200.0 on the master updates within one PROFINET update cycle (default 1 ms).
• Disconnect the PROFINET cable to the I-Device. The master's OB82 must fire; the SF LED on the master must illuminate; the I-Device's outputs must enter substitution state.

6. Method B — FB Instance Separation (Single CPU, One IM151-3 PN)

This method applies when Station 2 has been reduced to an IM151-3 PN head module with no program execution. The master IM151-8 PN/DP runs one consolidated OB1, and each filler's logic is encapsulated in an FB that takes its I/O references as formal parameters. Each call uses its own instance DB and binds the formal I/O parameters to a different absolute address.

6.1 FB Definition

FUNCTION_BLOCK FillerControl
VAR_INPUT
  i_FillerHome  : BOOL;   // home limit switch
  i_StartCmd    : BOOL;   // HMI start command
  i_StopCmd     : BOOL;   // E-stop / HMI stop
END_VAR
VAR_OUTPUT
  q_FillerOpen  : BOOL;   // pneumatic valve
  q_FillerRun   : BOOL;   // run indicator
END_VAR
VAR
  s_State       : INT;    // 0=idle, 1=running, 2=dwell, 3=close
  s_Timer       : TON;    // dwell timer
END_VAR
BEGIN
  // ... step sequence using only formal parameters
END_FUNCTION_BLOCK

6.2 Instance Calls in OB1

// Station 1 instance - addresses default to byte 0
CALL "FillerControl" , "DB_Filler_1"
  i_FillerHome := I0.0
  i_StartCmd   := M10.0
  i_StopCmd    := M10.1
  q_FillerOpen := Q0.0
  q_FillerRun  := Q0.1;

// Station 2 instance - bind to different peripheral bytes
CALL "FillerControl" , "DB_Filler_2"
  i_FillerHome := I4.0    // IM151-3 PN slot 1, byte 0 of Station 2
  i_StartCmd   := M20.0
  i_StopCmd    := M20.1
  q_FillerOpen := Q4.0    // IM151-3 PN slot 1, byte 0 of Station 2
  q_FillerRun  := Q4.1;

6.3 Why the FB Pattern Works

The FB has no absolute I/O references inside its code body. The step sequence, timers, counters, and state machine live entirely in the instance DB's static variables. Two calls to the same FB produce two independent state machines. The output Q0.0 on the first call and the output Q4.0 on the second call resolve to physically separate PROFINET slots in the master's process image, which in turn resolve to physically separate I/O modules on the two ET200S stations.

7. Method C — Peripheral Address Remap in HW Config

Method C is the lowest-effort path when Station 2 is reduced to an IM151-3 PN: leave both stations' programs almost untouched, but remap Station 2's peripheral byte addresses in the master's HW Config so they do not collide with Station 1.

1. In the master CPU's HW Config, locate the IM151-3 PN head module (drag from catalog PROFINET IO > ET200S > IM151-3 PN).
2. Place the IM151-3 PN on the master's PROFINET subnet. Assign device name et200s-station2 and IP 192.168.0.21.
3. Slot 1 of the IM151-3 PN holds Station 2's first I/O module. Double-click the module and set its Start Address to 4 (decimal) instead of the default 0.
4. Slot 2 (next I/O module) inherits the next free address: 5 for digital, 512 for analog, etc.
5. Save, compile, download.

Symbol Table Edit (Method C)

Open the master's Symbol Table and edit every Station 2 symbol:

The analog channel remap follows the same rule: PIW 304 / PQW 304 in Station 1, PIW 512 / PQW 512 in Station 2. STEP 7 reserves the analog address space at 256-word boundaries; if Station 1 already uses 304..320, move Station 2 to the next free 256-word block.

8. OB, FC, FB, DB Conflict Resolution

When two identical programs are merged into one CPU, every named block collides. The CPU will accept whichever block was downloaded last; the other block's content is silently discarded. The following table enumerates the affected blocks and the resolution rule.

9. PROFINET Device Name and IP Address Plan

Each PROFINET node must have a unique device name and IP address. The master IM151-8 PN/DP itself owns the PROFINET device name of the IO Controller; the IM151-3 PN head module of Station 2 owns its own device name.

Reserved address space: 192.168.0.1–9 for engineering stations (PG/PC), 192.168.0.10–29 for PROFINET devices, 192.168.0.50–59 for HMI/SCADA, 192.168.0.250 for router, 192.168.0.255 broadcast.

10. STEP 7 Classic Procedure for Method C (Field-Proven Sequence)

1. Archive both stations' STEP 7 projects. File > Archive.
2. Open the master CPU's HW Config. Drag the IM151-3 PN from the catalog into the PROFINET subnet.
3. Set device name and IP per Section 9.
4. Insert the I/O modules under the IM151-3 PN exactly in the slot order they exist on the physical station.
5. Edit Start Address on the first I/O module to 4 (digital) or 512 (analog).
6. Save and compile. STEP 7 will report any address collisions — fix them before download.
7. Download HW Config to the master CPU only. PLC > Download to Target.
8. Use PLC > Assign PROFINET Device Name to push the device name to the IM151-3 PN head module. Confirm the BF LED on the IM151-3 PN extinguishes within 5 seconds.
9. Cycle power on the IM151-3 PN to make the device name persistent in flash.
10. Download the symbol table only (not the program) and observe the master's online view: I4.0 should mirror the physical input wired to Station 2.

11. TIA Portal Procedure (TIA V15.1+)

1. Open the project. Select the master CPU in the Project Tree.
2. In the Device view, expand the master's PROFINET interface. Drag IM151-3 PN from the catalog (right pane) onto the PROFINET subnet of the master.
3. Right-click the IM151-3 PN > Properties > PROFINET interface > Ethernet addresses. Set IP and PROFINET device name.
4. Right-click the IM151-3 PN > Properties > Slot assignment. For each module slot, change the I/O start address: digital modules > 4; analog modules > 512.
5. Compile and download the device configuration.
6. Use Online > Assign PROFINET device name to write the name to the head module.
7. Open the master PLC's Symbol Table. Add the Station 2 symbols pointing at the new addresses.
8. Download the program blocks. Trigger a download of the symbol table by right-clicking it > Compile > Download to device.

12. Verification, Diagnostics, and Troubleshooting Matrix

12.1 Visual Verification

12.2 Web Server Diagnostics

The IM151-8 PN/DP web server (default http://192.168.0.10) exposes:

• Information > Module Identification — order number, firmware version, serial number
• Information > PROFINET Diagnostics — port state, link speed, frame errors
• Diagnostics > Diagnostic Buffer — chronological OB entries
• Information > Connected I/O — slot-by-sl slot module status

Cross-reference the diagnostic buffer with the PROFINET device name of the failed station to isolate the failure to the right head module.

12.3 PRONETA and Topology Check

Use Siemens PRONETA (free tool) to scan the PROFINET subnet, view the discovered device names, and verify that the IM151-3 PN appears with the correct name and IP. PRONETA also performs an I/O test that lets you force individual output bits on Station 2's modules — useful for verifying Method C address remapping.

12.4 Troubleshooting Matrix

13. PROFINET Performance and Update Time

PROFINET update time on the IM151-8 PN/DP / IM151-3 PN combination is configurable per device in HW Config under PROFINET interface > Real-time settings > Update time. Default is 1 ms. For a two-station filler, 1 ms is adequate for digital I/O and sufficient for analog if update time is increased to 4 ms.

The watchdog time is automatically 3 × the update time per the PROFINET specification. Do not configure the watchdog manually; doing so is a common source of unnecessary OB86 (rack failure) entries.

14. Safety Considerations

This article covers standard (non-failsafe) integration. For functional safety (F-CPU, PROFIsafe), the IM151-8 PN/DP F-variant and the F-I/O modules (e.g., 6ES7138-4FA00-0AB0 PM-E F, 6ES7136-4BA00-0AB0 4 F-DI, 6ES7136-4CA00-0AB0 4 F-DO) are required. PROFIsafe addresses are assigned in HW Config and must be unique per slot. Consolidating two F-CPUs into one F-CPU changes the PROFIsafe destination address plan; the TÜV-certified safety program must be re-validated.

15. Commissioning Checklist

• ☐ Both ET200S stations' HW Configs archived
• ☐ Master CPU configured with both PROFINET devices (master's own PROFINET subnet, plus Station 2 as I-Device or IO Device)
• ☐ All peripheral addresses verified non-overlapping (Method C) or encapsulated (Method B / A)
• ☐ PROFINET device names assigned and persistent (cycled power)
• ☐ Symbol table reviewed; Station 2 symbols renamed for clarity (Filler2_*)
• ☐ OB82 / OB86 present in master program
• ☐ All FC/FB/DB number conflicts resolved (renamed or re-numbered)
• ☐ PRONETA scan shows both stations with correct device names
• ☐ Web server accessible on master and Station 2 (if Method A)
• ☐ Force test of one output per station; verify the correct physical output responds
• ☐ Cable test on the PROFINET ring / daisy-chain
• ☐ Diagnostic buffer empty after a 10-minute soak