Configuring ET200M Distributed I/O Addresses in STEP 7 and TIA

Overview

The Siemens ET 200M is a modular distributed I/O station that accepts standard SIMATIC S7-300 signal modules (SM), function modules (FM), and communications processors (CP) on a backplane bus terminated by an interface module (IM 153). It connects to a higher-level controller — typically a SIMATIC S7-300, S7-400, S7-400H, or ET 200S CPU — over PROFIBUS-DP (via IM 153-1/-2/-2AR) or PROFINET IO (via IM 155-5 PN). Each ET 200M can hold up to 8 or 12 signal modules (slot count depends on the interface module variant) and is hot-swappable in most configurations.

This article addresses two recurring engineering questions when commissioning an ET 200M with one DI 32 module and seven AI 8 modules in an S7-400H system:

1. What is the correct I-address for each module, and how is the address range generated by HW Config?
2. What is the difference between OB1 Process Image (PI) and Process Image Partition (PIP), and which one should be assigned?

The procedure applies equally to STEP 7 V5.7 (HW Config) and to TIA Portal V20 (Devices & Networks). Differences between the two toolchains are called out explicitly.

Prerequisites

Before configuring the addresses, confirm the following items are available and installed:

• STEP 7 V5.7 with S7-400H option package installed, or TIA Portal V18/V19/V20 with SIMATIC S7-400H HSP.
• SIMATIC ET 200M hardware manual and the IM 153-x operating instructions (PDF on the Siemens support portal).
• ET 200M rack (e.g., 6ES7195-1GA00-0XA0 for active backplane, or 6ES7195-1GF30-0XA0 for BM 2x40).
• IM 153-2AR03 (6ES7153-2AR03-0XA0) for redundant PROFIBUS-DP connection to an S7-400H.
• DI 32 module, order number specific to voltage (e.g., 6ES7321-1BL00-0AA0 for 32×24 V DC sink input, or 6ES7321-1EL00-0AA0 for 32×120 V AC).
• AI 8 module matching the signal type: 6ES7331-7KF02-0AB0 (8×AI, 12-bit, ±10 V / 0–10 V / 4–20 mA), 6ES7331-7NF10-0AB0 (8×AI, 16-bit, high-resolution), or 6ES7331-7PF01-0AB0 (8×RTD/TC).
• GSD file for the IM 153-2AR03 (Siemens standard: siem80d0.gsd for PROFIBUS) — already included in the STEP 7 hardware catalog under PROFIBUS-DP > ET 200M.
• Programming device with MPI/PROFIBUS or Ethernet/PROFINET interface for online access.

Hardware Configuration of the ET 200M in STEP 7

Launch SIMATIC Manager and open the S7-400H station. Switch to HW Config and insert a DP slave of type ET 200M on the PROFIBUS(1) subnet. The catalog path in STEP 7 V5.7 is:

PROFIBUS-DP > ET 200M > IM 153-2AR03 (6ES7 153-2AR03-0XA0)

Drag the IM onto the PROFIBUS line. The IM 153-2AR03 is the redundant PROFIBUS-DP variant explicitly designed for S7-400H — it occupies two PROFIBUS addresses (one per channel) and is treated as two DP slaves. Place the IM twice if you also want to add the IM 153-1 (single-channel) variant for non-redundant stations. The official manual is available at ET 200M Operating Instructions (PDF).

Once the IM is placed, a slot table opens with slots 1 through 11 (or 1 through 12, depending on firmware). Click on each slot in order and drag the corresponding module from the catalog ET 200M > DI/DO > SM 321 or ET 200M > AI/AO > SM 331 into the slot. The slot numbering for the requested configuration is:

The exact start address depends on the modules placed before the AI cards. When only the DI 32 occupies slot 4, the AI cards begin at the next free word boundary after the digital range — which is PIW 512 for the standard STEP 7 default. This is not a coincidence: STEP 7 reserves the first 512 bytes (0–511) for the central I/O of the CPU rack and the distributed I/O of any station that has been configured earlier. The first available byte after byte 511 is byte 512, i.e. PIW 512.

How STEP 7 Generates the Default Address

When you place a module in HW Config, the editor performs these steps in order:

1. Calculates the module's address width in bytes. DI 32 = 4 bytes input (I 0.0 … I 3.7). AI 8 = 16 bytes input (PIW 512 … PIW 527, i.e. 8 channels × 2 bytes).
2. Searches the project's free address range for the lowest unused byte at the boundary required by the module type (byte boundary for DI, word boundary for AI).
3. Writes the result to the Addresses column of the slot table.

The default addresses shown in the screenshot of the original question — IB 0 and PIW 512 — are therefore correct and unique. You do not need to type a different value unless you are aligning to a customer address plan, integrating two previously independent projects, or matching a Profibus-DP slave that requires a fixed address.

Hardware Configuration in TIA Portal

In TIA Portal V18/V19/V20 the catalog path is Distributed I/O > ET 200M > Interface modules > IM 153-2AR PN HF (6ES7153-2AR10-0XA0) for PROFINET, or PROFIBUS-DP > ET 200M > IM 153-2AR03 for PROFIBUS. The configuration flow is documented in the TIA Portal help: Configuring an ET 200M — TIA Portal V20. The address generation rules are identical: the DI 32 occupies IB 0 … IB 3 and the AI 8 modules start at PIW 512 by default.

Process Image — OB1 PI vs PIP

Each input and output module can be assigned to one of two process-image update mechanisms:

For a standard ET 200M with DI 32 and AI 8 modules in an S7-400H system, the recommendation is:

1. Leave DI 32 in OB1 PI (PIP = 0) if the digital inputs are not time-critical — e.g. push-buttons, limit switches, contactor feedback.
2. Assign AI 8 modules to Process Image Partition 1 (PIP 1) if the analog values are consumed in a time-controlled OB such as OB35 (e.g. for a 100 ms controller), and call UPDAT_PI / UPDAT_PO explicitly with PIP 1, or rely on the implicit update done by the system at the start/end of the partition-owning OB.

The configuration is set in HW Config by double-clicking the module → Addresses tab → Process Image drop-down. In TIA Portal, navigate to Properties > I/O addresses > Process image and select Automatic update (OB1 PI) or Process image partition (PIP n).

Address Layout for the Reference Project

Final recommended address map for the example project (S7-400H, one ET 200M via IM 153-2AR03 on PROFIBUS(1) with PROFIBUS address 4, DI 32 at slot 4, AI 8 at slots 5–11):

Total digital input area: 4 bytes (32 bits). Total analog input area: 112 bytes (56 words / 56 channels). The combined I-address range 0 … 625 lies entirely within the default process image input (PII) of the S7-400H CPU, which is 8 192 bytes for CPU 412H/414H and 16 384 bytes for CPU 416H/417H — well within limits.

S7-400H-Specific Considerations

When the ET 200M is connected to an S7-400H redundant pair, additional rules apply:

• Interface module: Use IM 153-2AR03 (6ES7153-2AR03-0XA0) or IM 153-2FO AR03 (6ES7153-2BB30-0XA0) for fiber-optic PROFIBUS. Single-channel IM 153-1 is not supported in H systems.
• PROFIBUS address: Each redundant channel uses one PROFIBUS address. The IM occupies two addresses, e.g. 4 and 5, and the master treats them as one logical DP slave.
• Redundancy behavior: The S7-400H firmware cyclically tests both PROFIBUS lines. On failure of the primary line, the standby CPU takes over within <100 ms; the ET 200M continues to be addressed via the surviving channel without losing I/O updates — provided the modules do not have their own redundancy limitation.
• Address uniqueness across H-mirrored stations: If both H-CPUs run their own ET 200M station at the same PROFIBUS address (mirrored I/O), STEP 7 will warn about duplicate addresses. In an S7-400H the addresses are physically shared, but the symbolic names must be unique inside the S7 program.

Detailed redundancy commissioning steps are in the S7-400H manual on the Siemens support portal: S7-400H — Fault-tolerant Systems.

Step-by-Step: Verify the Address in HW Config

1. Open the S7-400H project in SIMATIC Manager and double-click Hardware in the left tree to launch HW Config.
2. Click the ET 200M station on the PROFIBUS line; the slot table appears.
3. Click slot 4. In the lower half of the editor confirm: Order number matches the physical SM 321, I address reads 0 (start byte), Process image reads OB1 PI.
4. Click slot 5. Confirm: Order number matches the SM 331 variant, I address reads 512, Process image reads OB1 PI or PIP 1 as required.
5. Repeat for slots 6–11 and verify contiguous address ranges 528, 544, 560, 576, 592, 608.
6. Select Station → Save and Compile (Ctrl+S). The action recompiles the hardware configuration and writes the system data blocks (SDB).
7. Download the hardware configuration to the active CPU (H-CPU 0 in RUN). The redundant partner receives the new SDBs automatically via the redundancy link.

Step-by-Step: Verify Online on the Live System

1. Connect the programming device to the MPI/DP or Ethernet port of the active CPU.
2. Open Monitor/Modify from HW Config (right-click the ET 200M station → Monitor/Modify).
3. Force I 0.0 by toggling the physical input. Confirm the bit toggles online.
4. Watch PIW 512 — apply a known voltage (e.g. 5.000 V on a ±10 V range) to channel 0. The reading should jump to a value near 27648 (full scale for the bipolar ±10 V range on SM 331 6ES7331-7KF02).
5. Cycle the PROFIBUS connector on the active line. The IM 153-2AR03 should switch to the redundant channel within ≤300 ms, the SF LED should remain off, and the process image should keep updating.

Troubleshooting Matrix

Edge Cases and Field-Proven Caveats

• Default address shift after a CPU change. Replacing an S7-400H CPU 414-4H with a CPU 416-4H can shift the start of the distributed I/O because the central I/O area of the 416-class CPU is larger. Always re-check the slot table after a CPU swap.
• Merging two projects. If you import an S7 project that already had its own ET 200M at the same PROFIBUS address, STEP 7 will report a duplicate PROFIBUS address. Resolve it by changing the rotary switch on one IM 153 module before download.
• Hot-swap of an AI 8 module. The IM 153-2AR03 supports hot-swap of every module except the IM itself. During hot-swap the address range remains valid; the cyclic process image freezes for the affected slots until the new module finishes initialization. CPU 41xH OB70 (redundancy loss) does not fire for module hot-swap.
• PROFINET variant. When migrating to PROFINET with IM 155-5 PN (6ES7153-4BA00-0XB0 or newer -5BA02), the device name (e.g. et200m-h1) must be assigned via the PRONETA tool or the topology editor. The I-addresses remain the same as in the PROFIBUS configuration; the PROFINET device number is separate from the I-address.
• Firmware update of the IM. Use the SIMATIC Automation Tool or the TIA Portal online → Update firmware function. The IM firmware must be compatible with the configured HW Config version — STEP 7 V5.7 supports IM 153-2AR03 up to firmware V8.x; TIA Portal V20 supports the latest.
• Address space reserved by CPs. If you also place an S7-300 CP 343-1 in slot 2, the CP occupies its own input area, which can shift the AI start address. Plan slot 2 carefully and verify the addresses after the CP is placed.

Programming Example: Reading PIW 512 in OB35

The following STL snippet reads the eight AI channels of slot 5 inside a 100 ms time-controlled OB35, applies a 1-of-8 demultiplex on PIP 1, and stores the scaled value into a shared DB.

// OB35 — cyclic interrupt, 100 ms
// PIP 1 must be assigned to the AI 8 modules
// Scaled values land in DB200 (REAL, 56 channels)

      L     PIW  512           // slot 5, channel 0
      ITD
      DTR
      L     2.764800e+04       // 27648 = full scale 10 V / 20 mA
      /R
      T     DB200.DBD0         // scaled 0.0 .. 1.0

      L     PIW  514           // channel 1
      ITD
      DTR
      L     2.764800e+04
      /R
      T     DB200.DBD4
// ... repeat for channels 2..7, slots 6..11

Or in Structured Text (TIA Portal SCL):

// FB "Ai8Scale" — scale AI8 module channels to engineering units
// Input: iRaw ARRAY[0..7] OF INT  (PIW 512..527 etc.)
//        rFullScale REAL := 27648.0
// Output: rEgu ARRAY[0..7] OF REAL

FOR i := 0 TO 7 DO
    IF iRaw[i] < -32768 THEN iRaw[i] := -32768; END_IF;
    IF iRaw[i] >  32767 THEN iRaw[i] :=  32767; END_IF;
    rEgu[i] := INT_TO_REAL(iRaw[i]) / rFullScale;
END_FOR;

Verification Checklist

• [x] HW Config compiles without errors or warnings.
• [x] All SM 321 / SM 331 order numbers match the physical modules.
• [x] I-addresses are unique and within the CPU PII range.
• [x] Process Image selection is documented: DI = OB1 PI, AI = PIP 1.
• [x] IM 153-2AR03 firmware version matches the GSD/STEP 7 catalog version.
• [x] Online Monitor/Modify shows correct input values.
• [x] PROFIBUS redundancy test passes: disconnect channel A, I/O keeps updating via channel B within 300 ms.
• [x] DIAGNOSE buffer free of Module faulty and Station failure entries.

Notes for Migration to TIA Portal

If the project is later migrated to TIA Portal V20 from STEP 7 V5.7, use Project → Migrate project. The migration preserves the I-addresses and the process image assignment. The only manual fix typically required is the PROFINET device name for the IM 155-5 PN variant, if the station is upgraded from PROFIBUS to PROFINET. Reference documentation for the migration is included in the TIA Portal help: Configuring an ET 200M in TIA Portal.