Configuring Active Bus Modules and Redundant IM 153-2 Interfaces in PCS 7 HW Config

In SIMATIC PCS 7 HW Config, designing a redundant distributed I/O architecture using an S7-400H / CPU 414-5H controller and ET 200M stations with dual IM 153-2 interface modules (redundant PROFIBUS DP) cannot be accomplished by placing two separate IM 153-2 modules manually into a standard DIN rail rack. In STEP 7, redundancy requires the active backplane bus module (BM 2xIM153-2). To configure this correctly, do not create two separate interface entries; instead, drag the single catalog entry 'IM 153-2 HF Redundant' from 'PROFIBUS-DP > ET 200M' onto DP Master System 1. In the module properties under the 'Redundancy' tab, select 'Connection to 2 DP master systems' and select the redundant DP line from CPU 2. HW Config will automatically generate the dual-interface rack with active backplane bus modules.

Executive Summary

Designing high-availability fieldbus architectures in SIMATIC PCS 7 requires redundant communications paths between fault-tolerant AS controllers (S7-400H / CPU 410-5H) and distributed ET 200M I/O stations. A frequent stumbling block for engineers configuring hardware in STEP 7 HW Config is attempting to manually place two IM 153-2 High Feature interface modules side-by-side on a standard 300/400 rack. HW Config strictly prohibits multiple interface modules on a standard rail, leading to confusion. Understanding that redundant ET 200M stations require the active backplane bus framework (BM 2xIM153-2 / 6ES7195-7HD10-0XA0) and utilizing the integrated 'IM 153-2 Redundant' catalog profile allows flawless hardware synthesis.

Architecture and Fundamental Mechanics

The hardware and software architecture of redundant ET 200M distributed I/O in SIMATIC PCS 7 is governed by active bus module mechanics:

The Active Backplane Bus Architecture (BM 2xIM153-2):
* A standard S7-300 / ET 200M backplane uses passive U-shaped bus connectors. Passive backplanes do NOT support redundancy or hot-swapping.
* High-availability PCS 7 configurations mandate an active backplane bus rail with hot-swappable bus modules:
- Slot 1 & 2: Active Bus Module BM 2xIM153-2 (6ES7195-7HD10-0XA0), which hosts two physical IM 153-2 modules side-by-side.
- Subsequent Slots: Active Bus Modules BM 2x40 or BM 1x80 (6ES7195-7HB00-0XA0), which host I/O modules.
- The active bus module mechanically routes PROFIBUS DP Line 1 to IM 153-2 (A) and Line 2 to IM 153-2 (B), while providing an internal multiplexer to the shared I/O backplane.
The Software Representation in HW Config:
* HW Config models the two physical interface modules as a single logical distributed I/O station with dual network attachments.
* Attempting to drag two independent ET 200M stations from the catalog creates two distinct stations that cannot share I/O cards.
* The correct catalog element is IM 153-2 HF Redundant (or standard IM 153-2 HF configured with redundant master system links).
Redundant Switching Mechanics:
* One IM 153-2 acts as the Active Master; the second acts as the Standby Listener.
* If Line A or IM A suffers a wire break, power loss, or transceiver failure, IM B takes over the active backplane bus within 30 milliseconds—completely bumpless to active process control.

Step-by-Step Implementation Procedure

Follow these procedures to configure a redundant ET 200M station in PCS 7 HW Config:

Configure S7-400H Hardware with Dual DP Masters:
* In SIMATIC Manager Component View, open HW Config for the SIMATIC H Station.
* Verify that both CPU 414-5H / CPU 410-5H controllers (Rack 0 and Rack 1) have their integrated PROFIBUS DP interfaces or CP 443-5 Extended modules configured.
* Ensure both CPUs are connected to their respective PROFIBUS networks:
- CPU 0 connected to PROFIBUS(1): DP master system (1)
- CPU 1 connected to PROFIBUS(2): DP master system (2)
Insert the Redundant ET 200M Station from Catalog:
* In the HW Config hardware catalog pane, navigate to:
PROFIBUS DP > ET 200M > IM 153-2 (e.g., 6ES7 153-2BA02-0XB0 or 6ES7 153-2BA10-0XB0).
* Select the module and drag it onto DP master system (1) of CPU 0.
* Assign a PROFIBUS DP address (e.g., Address 3).
Configure Redundancy Properties:
* Right-click the newly inserted IM 153-2 station on the network line and select Object Properties.
* Navigate to the Redundancy tab.
* Check the radio button Connection to 2 DP master systems.
* In the redundant partner dropdown, select DP master system (2) of CPU 1.
* Verify that the partner PROFIBUS address is assigned (typically identical, Address 3).
* Click OK.
* HW Config automatically redraws the station: two red PROFIBUS lines now attach to the ET 200M station from both CPU racks.
Populate I/O Modules in the Active Backplane:
* Double-click the ET 200M rack icon to open its slot table.
* Slot 1 and Slot 2 are automatically reserved for the dual IM 153-2 modules.
* In Slots 4 through 11, insert the required S7-300 signal modules (SM 321 DI, SM 322 DO, SM 331 AI, SM 332 AO).
Compile and Download Hardware:
* Select Station > Save and Compile.
* In the H-station download dialog, download the hardware configuration to both CPU 0 and CPU 1.
* Verify that the active backplane bus module compiles without address collisions.

Verification

After downloading, observe the physical ET 200M rack. Confirm that both IM 153-2 modules show solid green RUN LEDs and that the ACT LED is illuminated on IM A (indicating active master) while extinguishing on IM B (standby). Disconnect the PROFIBUS cable from IM A; verify that IM B instantly illuminates its ACT LED without an AS STOP or I/O glitch, and that the AS diagnostic buffer records an OB86 rack redundancy switchover event.

Limitations and Operational Precautions

Redundant ET 200M configurations strictly require the physical active bus rail and BM 2xIM153-2 active bus modules. You cannot implement PROFIBUS redundancy using standard passive bus connectors. Verify that the PROFIBUS transmission speed (baud rate) is identical on both DP master systems (typically 1.5 Mbps).

Engineer FAQ

Why can't I place two IM 153-2 modules into adjacent slots manually in HW Config?

In STEP 7 HW Config, an ET 200M station represents a single logical chassis. Redundancy is enabled via the station's Redundancy properties tab, which automatically manages dual interface slots on active bus modules.

What active bus module order number is required for dual IM 153-2?

The active bus module for redundant IM 153-2 is 6ES7195-7HD10-0XA0 (BM 2xIM153-2).

Can I use standard S7-300 I/O modules with redundant IM 153-2?

Yes. Standard S7-300 SM modules (DI, DO, AI, AO) are fully supported on the active backplane bus behind redundant IM 153-2 interfaces.

How long does an IM 153-2 switchover take during a cable break?

Switchover between redundant IM 153-2 modules occurs within approximately 30 milliseconds, well within standard process tolerance and watchdog thresholds.