Siemens ET 200M IM 153-2 Redundant PROFIBUS Configuration

Overview of ET 200M Redundant PROFIBUS Architecture

The SIMATIC ET 200M is a modular, distributed I/O station that operates on PROFIBUS DP. When deployed against an S7-400H redundant controller, two IM 153-2 interface modules are required to provide fault-tolerant I/O access: one IM 153-2 on PROFIBUS DP1 (H-station CPU 0) and a second IM 153-2 on PROFIBUS DP2 (H-station CPU 1). The redundant pair is treated by the H-CPU as a single logical station, although the hardware layout uses two physically separate interface modules on two physically separate bus segments.

The most common confusion when reading the S7-400H manual diagrams is whether the two IM 153-2 boxes represent a single module with two PROFIBUS ports, or two discrete single-port IM 153-2 modules. In every documented Siemens configuration, the diagram shows two discrete IM 153-2 modules, each with a single PROFIBUS DP port, mounted on a shared active backplane bus. The redundancy is achieved at the bus segment level (DP1 and DP2), not at the port level of a single device.

IM 153-2 Interface Module Variants and Part Numbers

Several IM 153-2 variants exist, and selecting the wrong one will prevent STEP 7 / TIA Portal from accepting the redundant bundle. Use the table below to identify each variant.

The bundle MLFB 6ES7153-2AR03-0XA0 is a factory pre-paired redundancy kit. It contains two IM 153-2HF modules (-2BA02) plus one IM/IM bus module (6ES7195-7HD10-0XA0) on a single shipment. The two interface modules share the same active backplane bus, and STEP 7 / TIA Portal inserts them as a single logical station when configured against an S7-400H.

The Redundant Bundle 6ES7153-2AR03-0XA0 in Detail

The redundant bundle is the recommended hardware for new S7-400H installations because the two IM 153-2HF modules are matched at the factory for timing characteristics, firmware revision, and PROFIBUS node behavior. Using two separately purchased modules from different lots can result in asymmetric switchover times, which may surface as DP diagnostic alarms during H-CPU failover.

The IM/IM bus module 6ES7195-7HD10-0XA0 is the key piece of hardware that allows two IM 153-2 modules to sit on the same ET 200M station. It provides the slot-to-slot interconnect that the redundant pair needs to share slot addressing and to coordinate module diagnostics.

Why Two IM 153-2 Cannot Be Inserted on the Same Logical PROFIBUS Segment

STEP 7 (HW Config) and TIA Portal (Devices & Networks) will reject an attempt to drop two standalone IM 153-2 modules on the same PROFIBUS DP subnet as a single ET 200M station. The reason is structural:

1. PROFIBUS DP supports one IM per logical station per bus segment.
2. An ET 200M station is identified by a single PROFIBUS address. The H-CPU must see the station twice — once on DP1 (CPU0) and once on DP2 (CPU1) — to obtain redundancy.
3. Two IM 153-2 on the same segment at the same PROFIBUS address would produce address collision. Two IM 153-2 at different PROFIBUS addresses on the same segment would not share the backplane and would be treated as two independent stations, defeating redundancy.

The correct topology is therefore: one IM 153-2 on DP1 with PROFIBUS address A, one IM 153-2 on DP2 with the same PROFIBUS address A, both mounted on the active backplane bus. The redundancy is at the bus and CPU level, not at the segment level.

Active Backplane Bus versus Conventional Profile Rail

ET 200M redundancy is only possible on the active backplane bus. The conventional profile rail with bus connectors between modules does not provide the slot continuity that two IM 153-2 modules need.

If you attempt to mount the redundant bundle on a conventional rail, STEP 7 / TIA Portal will display a configuration error stating that the IM 153-2 redundancy pair requires an active bus module. Replace the rail before commissioning.

S7-400H Redundant I/O PROFIBUS Topology

Below is the canonical topology. Each H-CPU owns one PROFIBUS DP subnet, and each subnet terminates at one IM 153-2 of the redundant pair. The I/O modules between the two IM 153-2 heads are physically shared on the active backplane.

Both IM 153-2 heads use the same PROFIBUS address (typically 3, 4, or 5 depending on slot reservation). The H-CPU cycles between DP1 and DP2; whichever IM 153-2 is active drives the I/O update. On a CPU or bus failover, the standby IM 153-2 takes over within the configured redundancy switchover time.

Hardware Configuration in STEP 7 / TIA Portal

The redundant bundle is inserted as a single station object, even though it represents two physical IM 153-2 modules. The procedure below applies to both STEP 7 V5.x (HW Config) and TIA Portal V16+.

1. Open the project, select the S7-400H station, and open Devices & Networks.
2. Right-click the DP1 subnet and choose "Insert New Station > ET 200M".
3. From the hardware catalog, navigate to PROFIBUS DP > I/O > ET 200M and select the IM 153-2 variant matching your bundle (typically 6ES7153-2BA02 for the HF modules in the redundant bundle).
4. Assign the PROFIBUS address. The same address must be assigned to both DP1 and DP2 instances of the station.
5. On DP2, right-click and insert the same ET 200M station. STEP 7 / TIA Portal will detect that an identical address already exists and bind it as the redundant partner.
6. Insert signal modules (SM321, SM322, SM331, SM332, SM334) into slots 4 through 11 of the ET 200M. Slot configuration must be identical on both IM 153-2 views.
7. Open the IM 153-2 properties, enable "Module replacement during operation" and confirm that the active bus module is recognized.
8. Compile and download to both H-CPUs.

PROFIBUS Address Assignment and Bus Parameters

PROFIBUS DP for ET 200M redundant operation should use the following recommended parameters. These values match the Siemens S7-400H redundant system manual defaults.

The PROFIBUS line length for 1.5 Mbit/s without repeaters is 200 m per segment. For longer runs, insert an RS 485 repeater (6ES7972-0AA01-0XA0) at each segment boundary. The H-CPU PROFIBUS interfaces are isolated, so DP1 and DP2 must use separate physical cables; do not bridge DP1 and DP2 with a repeater.

Module Replacement During Operation on the Redundant Station

The 'Module replacement during operation' function is enabled by default for IM 153-2 on an active backplane bus. When activated, individual signal modules may be pulled and replaced without stopping the CPU or interrupting the bus. This is critical for redundant I/O because the standby IM 153-2 keeps the process I/O updated while a module is being swapped.

Two configuration options control the function:

• Remove/insert interrupt enabled: the H-CPU receives OB83 / OB85 diagnostics whenever a module is removed or inserted. Recommended for most redundant applications.
• Remove/insert interrupt blocked: with the interrupt blocked, removal and insertion remain possible but no diagnostic OB is triggered. Use this only when OB83 / OB85 handling is undesirable.

See the TIA Portal V20 documentation for Module Replacement During Operation for the full configuration tree. The operating instructions manual (ET 200M Operating Instructions PDF) provides the field wiring and removal steps.

Diagnostic Buffer Entries and Common Fault Codes

Below are diagnostic buffer entries that field engineers report most often on redundant ET 200M stations.

The standard S7 diagnostic LED pattern on the IM 153-2 front panel helps localize the fault:

• SF (red): group fault — check diagnostic buffer.
• BF (red): bus fault on the PROFIBUS segment.
• ACT (green): active head — the IM is currently driving I/O.
• STBY (green on HF): standby head — redundant partner is driving I/O.

Troubleshooting Matrix for Redundant ET 200M

Field Commissioning Checklist

1. Verify MLFB 6ES7153-2AR03-0XA0 is the bundle actually delivered. Confirm both IM 153-2 heads and one IM/IM bus module are present.
2. Mount the active backplane bus (6ES7195-1GA00-0XA0 or length-appropriate variant). Standard 482 mm rail is insufficient.
3. Seat the IM/IM bus module (6ES7195-7HD10-0XA0) at the leftmost slot.
4. Install both IM 153-2HF modules (6ES7153-2BA02) onto the IM/IM bus module. Verify both seat with a positive click.
5. Install signal modules in slots 4 through 11 in the correct order.
6. Wire PROFIBUS connectors to both heads. Terminate the start and end of each DP segment only.
7. Set identical PROFIBUS address on both heads via the DIL switch or HW Config. Typical value: 3.
8. Download the HW Config to both H-CPUs.
9. Use the online diagnostic view to confirm "ACTIVE" on one head and "STANDBY" on the other.
10. Perform a failover test: pull the active PROFIBUS connector and confirm the standby IM 153-2 takes over without process interruption. Restore the connection and verify automatic re-synchronization.

Compatibility with S7-400H Firmware and Software Versions

Redundant ET 200M with IM 153-2HF (6ES7153-2BA02) is supported by the following baseline versions:

When migrating from a legacy IM 153-2 (-2AR02) to the HF variant (-2BA02), both IMs in the redundant pair must be upgraded together. Mixed-mode operation (one -2AR02 and one -2BA02) is not supported by STEP 7 and will produce a configuration error.

Notes on Power Supplies and Grounding for Redundant Stations

The redundant bundle is typically paired with two PS 307 power supplies (one per logical side) to match the H-system power architecture. Use one PS 307 (6ES7307-1EA01-0AA0, 5 A) per IM 153-2 if the I/O count is moderate. For higher load, specify PS 307 10 A (6ES7307-1KA02-0AA0).

Grounding must follow the ET 200M manual: connect the profile rail to functional earth (FE) at one point only, and apply the PROFIBUS cable shield at each connector clamp. The IM 153-2 provides a grounding screw on the front panel for this purpose. Floating grounds between DP1 and DP2 are acceptable because the H-CPU PROFIBUS interfaces are isolated, but the rack ground must be common to avoid ground-loop noise on analog SM331 channels.

Calculating I/O Update Time on the Redundant Pair

The I/O update time on the redundant pair is governed by the PROFIBUS cycle time plus the redundancy switchover overhead. Use the formula:

T_update = T_DP_cycle + T_switchover

Where T_DP_cycle is the standard PROFIBUS DP cycle time for the configured baud rate and number of slaves, and T_switchover is the redundancy transition time, typically 100 ms to 500 ms for IM 153-2HF, depending on H-CPU firmware and configured OB priority.

For a 1.5 Mbit/s PROFIBUS network with 16 slaves and 32 bytes of I/O per slave, T_DP_cycle is approximately 5–10 ms. Adding T_switchover of 200 ms gives a worst-case redundant update window of approximately 210 ms. This is acceptable for most process control loops with sample times above 500 ms; faster loops may need an S7-400H with PROFINET instead of PROFIBUS.

Differences Between the Bundle Drawing and the HW Config View

The S7-400H manual schematic and the actual STEP 7 / TIA Portal view differ visually. The manual typically shows two IM 153-2 boxes side by side on a single rail with two DP cables connecting to two CPU PROFINET/PROFIBUS ports. The HW Config / TIA Portal view shows a single ET 200M station object with one IM 153-2 entry, but with a redundant partner indicated via a property flag and a second instance on DP2. Both representations describe the same physical hardware.

This visual mismatch is the source of the most common engineer question on this topic: the diagram looks like two standalone IM 153-2 on a single DP segment, but the configuration tool insists on two separate DP segments. Trust the configuration tool: PROFIBUS redundancy for S7-400H requires two DP segments (DP1 and DP2), one IM 153-2 per segment, and a shared active backplane bus.

Migrating from PROFIBUS Redundancy to PROFINET Redundancy

If a migration to PROFINET is planned, the IM 153-2 cannot be reused. PROFINET redundant I/O uses the IM 153-4 PN (6ES7153-4BA00-0XB0) or IM 155-6 PN HF on ET 200SP. The wiring, addressing, and H-CPU configuration all change. The benefit is shorter switchover times (typically under 50 ms) and loss-free communication. Plan for a parallel-run validation window when migrating critical process lines.

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