ET 200M with S7-1500: Resolving CP340 Compatibility in TIA Portal

Overview

When an S7-400-based machine is migrated to the S7-1500 platform, every distributed I/O subsystem attached to the original PROFIBUS DP network must be re-evaluated for forward compatibility. The ET 200M is the most common distributed I/O station in this scenario because it physically accepts S7-300 signal, function, and communication modules on its backplane. However, the configuration technology of the ET 200M is still tied to the S7-300 automation system, and that limitation surfaces immediately when the GSD file is loaded into TIA Portal: many S7-300 sub-modules appear as catalog placeholders, and certain communication processors — most notably the CP340 — fail to appear at all.

This reference documents the root cause of that catalog gap, the correct interpretation of the IM 153-2AA00 article number used in the original hardware configuration, the exact GSD installation procedure, and the engineering path for replacing serial communication on a migrated line.

ET 200M Architecture and IM 153-2 Variants

The ET 200M distributed I/O station couples to a higher-level PROFIBUS DP master through an IM 153-x interface module. According to the official TIA Portal configuration documentation, the ET 200M configuration technology follows the S7-300 automation system: the IM 153-x acts as the DP slave interface, and the slots downstream of the IM are populated with S7-300 I/O modules. This is the architectural reason an ET 200M can host S7-300 SM, FM, and CP modules in the field — the station is essentially an S7-300 rack fronted by a PROFIBUS coupler.

The IM 153 family includes several variants that share the same footprint but differ in PROFIBUS capabilities, diagnostics, and firmware:

The article number fragment "153-2AA00" referenced in the source hardware configuration is interpreted as a placeholder within the GSD file pattern 6ES7 153-2BA*1-0XB0. The asterisk covers revisions where the digit changes — for example, BA01, BA02, BA10 — while the remainder of the article number stays constant. When a TIA Portal hardware catalog shows multiple IM 153-2 entries under "Other devices" after GSD installation, those entries correspond to the different positions of the asterisk in the placeholder.

Installing the ET 200M GSD File in TIA Portal

The ET 200M GSD package is published by Siemens under Industry Online Support entry ID 113498 ("PROFIBUS GSD files : ET 200M"). The GSD must be installed when the IM 153 variant is not part of the native TIA Portal hardware catalog.

Prerequisites

• TIA Portal V15.1 or later (V17 or V18 recommended for current ET 200M GSD revisions).
• Administrator rights on the engineering workstation for GSD installation.
• The ET 200M GSD archive (.zip) downloaded from Siemens Industry Online Support (entry ID 113498).

Installation Procedure

1. Open the TIA Portal project and switch to the Project view.
2. Select Options → Manage general station description files (GSD).
3. Browse to the directory containing the ET 200M GSD archive and select the file.
4. Confirm the installation. TIA Portal lists the parsed DP slave entries in the dialog.
5. Close the GSD manager. The IM 153-2 entries appear in the hardware catalog under Other field devices → PROFIBUS DP → ET 200M.

After installation, drag the IM 153-2 onto the PROFIBUS subnet in the Devices & Networks editor. The slot table then accepts S7-300 modules from the catalog — but only those modules that the GSD exposes. The catalog shown for an IM 153-2 installed via GSD is deliberately narrower than the catalog shown for an S7-300 central rack, because the GSD profile for distributed I/O does not include every S7-300 module entry.

The CP340 Compatibility Problem

The CP340 is a point-to-point serial communication processor designed for the S7-300 central rack. Its module firmware, parameter record layout, and diagnostic alarm interface are tied to the S7-300 system environment. When the CP340 is dragged into an ET 200M slot, three independent failure modes occur:

1. Catalog absence: The CP340 is not in the ET 200M GSD catalog because the GSD author has not declared it as a valid ET 200M sub-module. The slot remains empty in the configuration view.
2. Configuration rejection: If the CP340 is force-loaded from the S7-300 catalog into an ET 200M slot, TIA Portal raises a configuration error during compilation because the slot does not match the station profile.
3. Runtime failure: If the project is downloaded anyway, the IM 153 rejects the CP340 at PROFIBUS startup. The diagnostic buffer of the IM 153 records an "incorrect module in slot" entry, and the CP340 is not parameterized.

The CP340 is, mechanically and electrically, a module that fits the ET 200M backplane connector. Physical fit is not the same as configuration compatibility, and that distinction is the root cause of the catalog gap observed after GSD installation.

Root Cause: Why S7-300 Communication Modules Cannot Migrate Through ET 200M

The ET 200M GSD file declares the set of modules that the IM 153 is permitted to host in each slot. The declaration includes the article number, the diagnostic data length, the parameter record length, and the cyclic I/O length. Communication and function modules from the S7-300 family have parameter record and diagnostic structures that depend on the S7-300 backplane services. The IM 153 cannot provide those services because it terminates the backplane at its own PROFIBUS interface.

Three architectural constraints make the combination impossible:

• Diagnostic routing: CP and FM modules raise diagnostic interrupts that are addressed using S7-300 rack/slot logic. The IM 153 cannot translate those addresses to PROFIBUS DP-V1 diagnostic records.
• Parameter records: CP340 point-to-point parameters (baud rate, parity, character frame) are written using S7-300-specific record indices. The IM 153 only forwards a subset of record indices; CP-specific records are dropped.
• Cyclic I/O length: The CP340 occupies variable-length I/O areas that are sized by the host CPU at runtime. The IM 153 reserves slot I/O areas at PROFIBUS configuration time, before the CPU sees the module.

Together, these constraints mean that even if a workaround forces the CP340 into the configuration, no PROFIBUS master can establish useful cyclic communication with it. The module is effectively dead on arrival.

Migration Alternatives for Serial Communication

When the original S7-400 station used the CP340 for serial point-to-point traffic, three engineering paths are available for the S7-1500 migration. Each path has different hardware, software, and lifecycle implications.

Path 2 is the recommended migration when the serial cable length is short and the CPU has free slots. Path 3 is the recommended migration when the serial device is geographically separated from the control cabinet and the project already uses PROFINET. Path 4 is the recommended migration when the serial device is at end-of-life and the connected equipment is being modernized at the same time as the controller.

Step-by-Step: Correct ET 200M Configuration with S7-1500 Master

The procedure below documents the supported configuration path when an ET 200M with only signal modules (SM) must be retained under an S7-1500 CPU.

1. Add the S7-1500 CPU to the project. The CPU must have a PROFIBUS interface or be paired with a CP 1542-5 communications processor.
2. Add the ET 200M as a DP slave on the PROFIBUS subnet using either the native catalog entry (preferred) or the GSD-installed entry under Other field devices.
3. Select the IM 153 entry that matches the physical article number and firmware revision.
4. Populate the slots downstream of the IM with S7-300 SM modules (digital and analog I/O). These are the modules exposed by the ET 200M GSD.
5. Compile the hardware configuration. Verify that TIA Portal reports zero configuration errors and zero "module cannot be used in this slot" warnings.
6. Download the configuration to the CPU and the IM 153.
7. Verify PROFIBUS diagnostics using Online → Online & Diagnostics on the IM 153. Confirm the slot diagnostics show all configured SM modules in OK state.

If the project requires serial communication that the original S7-400 station implemented on a CP340 in the ET 200M, replace the CP340 with a supported configuration path from the table above. Do not attempt to drag the CP340 into the ET 200M slot.

Verification

After commissioning, verify the ET 200M configuration with the following checks:

• PROFIBUS DP-V0/V1 diagnostic buffer of the IM 153: No entries of class "incorrect module" or "parameterization error."
• Cyclic I/O update: Toggle a digital output on slot 4 of the ET 200M from the S7-1500 program and read back a digital input on slot 5. Confirm sub-millisecond round-trip latency on the DP cycle.
• Diagnostic interrupt propagation: Disconnect a field wire from an analog input module to provoke a wire-break diagnostic. Confirm the diagnostic alarm is reported to the S7-1500 OB82.
• Module replacement simulation: Power down the station, remove the IM 153, and reinsert. Confirm the station comes back online without manual re-parameterization.

If any check fails, refer to the troubleshooting matrix below.

Troubleshooting Matrix

Field-Commissioning Notes

Three field-proven caveats apply to ET 200M stations migrated to S7-1500 masters:

• Firmware consistency: If the cabinet contains IM 153 modules from different procurement batches, the firmware revisions may differ. Always read the physical article number and firmware version from the module label, not from the cabinet documentation. Mismatched firmware in a multi-IM installation produces intermittent station failures.
• GSD revision pinning: After installing the ET 200M GSD, pin the GSD revision in the TIA Portal project. A TIA Portal upgrade can silently replace the GSD with a newer revision and alter slot profiles, causing configuration errors after the next download.
• CP340 inventory disposition: CP340 modules removed from ET 200M slots during migration are not scrap. They can be re-used as spare parts for S7-300 stations that remain in service, or returned to inventory as S7-300-series communication modules. They are not ET 200M-compatible under any firmware revision.

For the authoritative configuration rules and supported module list, refer to the TIA Portal ET 200M configuration documentation and the IM 153-2 manual on Siemens Industry Online Support.