Siemens 6ES7155-6BU00-0CN0 ET 200SP PROFIBUS DP Upgrade

Product Overview

Siemens 6ES7155-6BU00-0CN0 ET 200SP PROFIBUS DP Upgrade: Seamless Transition from Legacy DP Systems

The Siemens 6ES7155-6BU00-0CN0 is the PROFIBUS DP Interface Module for the ET 200SP distributed I/O platform, designed to serve as the communication gateway between a PROFIBUS DP master — typically a Siemens S7-300, S7-400, or S7-1500 CPU — and the ET 200SP I/O station. For facilities currently operating aging ET 200S, ET 200M, or first-generation ET 200SP stations with discontinued interface modules, the 6ES7155-6BU00-0CN0 represents a validated, field-proven upgrade path that preserves existing wiring infrastructure, minimizes reprogramming effort, and dramatically reduces unplanned downtime risk.

When migrating from an ET 200S IM151-1 or IM151-3 PN interface module to the ET 200SP architecture, engineers frequently encounter concerns about backplane compatibility, terminal block re-use, and PROFIBUS address reassignment. The 6ES7155-6BU00-0CN0 addresses these concerns directly: it mounts on the ET 200SP BaseUnit BU-type rail, accepts standard PROFIBUS DP connectors (9-pin Sub-D), and supports baud rates from 9.6 kbps up to 12 Mbps — fully compatible with existing PROFIBUS segment configurations. The module’s GSD file integrates cleanly into STEP 7 Classic (v5.5 SP4 and above) and TIA Portal (v13 SP1 and above), allowing hardware configuration to be completed without rebuilding the entire network topology.

For plants running S7-300 CPUs such as the CPU 315-2 DP or CPU 317-2 DP as PROFIBUS masters, the transition to an ET 200SP station anchored by the 6ES7155-6BU00-0CN0 is particularly straightforward. The DP slave address is retained, the GSD-based I/O mapping remains consistent, and the physical footprint of the ET 200SP station is significantly more compact than the ET 200M or ET 200S predecessors — freeing valuable DIN rail space inside the control cabinet. This is especially relevant in retrofit projects where panel space is constrained and adding new I/O capacity without expanding the enclosure is a hard requirement.

Power supply integration is another critical consideration during migration. The 6ES7155-6BU00-0CN0 draws its logic supply from the ET 200SP internal bus, while field-side 24 VDC is distributed through the BaseUnit power bus. This architecture is compatible with existing Siemens SITOP PSU100S or PSU8600 power supply modules already installed in the cabinet, eliminating the need for additional power infrastructure. When replacing an ET 200S station, the existing 24 VDC feed can typically be re-terminated directly to the ET 200SP power module — such as the PM-E DC24V (6ES7138-4CA01-0AA0) — without rewiring the upstream distribution board.

Signal module compatibility is a key advantage of this upgrade. The ET 200SP ecosystem supports a wide range of digital and analog I/O modules — including the BaseUnit BU15-P16+A0+2D (6ES7193-6BP20-0DA0) and standard DI, DQ, AI, and AQ modules — that can be mixed freely on the same station. Facilities migrating from ET 200S signal modules can map existing I/O channel assignments to equivalent ET 200SP modules with minimal changes to the PLC program’s symbol table. In most cases, only the hardware configuration in TIA Portal or STEP 7 requires updating; the ladder logic or function block diagram controlling the I/O channels remains unchanged.

Communication reliability on the PROFIBUS DP segment is maintained through the 6ES7155-6BU00-0CN0’s integrated diagnostics. The module supports standard DP diagnostics (DPV0) and extended diagnostics (DPV1), enabling the master CPU to detect station faults, module removal events, and channel-level errors without additional programming. This is a direct functional equivalent to the diagnostic behavior of the IM151-3 PN or IM151-1 modules it replaces, ensuring that existing SCADA or HMI alarm logic — whether running on a Siemens TP700 Comfort panel or a WinCC Runtime system — continues to receive and display fault information correctly.

For projects involving a full system migration from S7-300/ET 200M to S7-1500/ET 200SP, the 6ES7155-6BU00-0CN0 fits naturally into the new architecture. The S7-1500 CPU acts as the PROFIBUS DP master via its CM 1542-5 communication module (6GK7542-5DX00-0XE0), and the ET 200SP station with the 6ES7155-6BU00-0CN0 as the DP slave integrates without protocol conversion. This eliminates the need for DP/PN link gateways or protocol converters, reducing both hardware cost and network latency. The result is a leaner, more maintainable architecture that supports future migration to PROFINET when the plant is ready.

On-site commissioning of the 6ES7155-6BU00-0CN0 follows the standard ET 200SP startup procedure: set the PROFIBUS address via the address selector switches on the module face, connect the PROFIBUS cable with the correct termination resistor enabled at segment endpoints, and perform a hardware scan in TIA Portal or STEP 7 to confirm the station is recognized. The module’s LED indicators (BF, SF, MAINT, and PWR) provide immediate visual feedback during startup, and the diagnostic buffer in the master CPU logs any configuration mismatches for rapid fault isolation. Total commissioning time for a pre-configured replacement station is typically under two hours for an experienced automation engineer.

Compatibility Comparison Table

Seamless Upgrade Solutions

A complete ET 200SP PROFIBUS DP station built around the 6ES7155-6BU00-0CN0 typically requires several complementary components sourced from the same Siemens ET 200SP ecosystem. The BaseUnit BU15-P16+A0+2D (6ES7193-6BP20-0DA0) provides the mechanical and electrical foundation for each I/O module slot, while the PM-E DC24V power module (6ES7138-4CA01-0AA0) distributes 24 VDC field power across the station bus. Digital input modules such as the DI 8x24VDC ST (6ES7131-6BF00-0BA0) and digital output modules like the DQ 8x24VDC/0.5A ST (6ES7132-6BF00-0BA0) cover the majority of discrete I/O requirements encountered in legacy ET 200S migrations.

For analog signal migration, the AI 4xU/I 2-wire ST (6ES7134-6GD01-0BA1) handles standard 4–20 mA and 0–10 V process signals without requiring signal conditioners or isolators in most applications. Where signal isolation is required — for example, when migrating thermocouple or RTD inputs from an ET 200M AI module — the AI 4xRTD/TC 2-/3-/4-wire HF (6ES7134-6JD00-0CA1) provides direct replacement capability with integrated cold junction compensation.

When the migration project also involves upgrading the PROFIBUS master from an S7-300 to an S7-1500, the CM 1542-5 PROFIBUS communication module (6GK7542-5DX00-0XE0) is the standard interface card that enables the S7-1500 CPU to act as a DP master, maintaining full backward compatibility with all existing DP slaves including the 6ES7155-6BU00-0CN0 station. Programming cable access during commissioning is facilitated by the SIMATIC USB PC Adapter (6ES7972-0CB20-0XA0), which provides USB-to-PROFIBUS connectivity for laptop-based TIA Portal or STEP 7 sessions without requiring a dedicated MPI/DP PCI card.

For HMI integration, the Siemens TP700 Comfort (6AV2124-0GC01-0AX0) connects to the S7-1500 or S7-300 master via PROFINET or MPI, and its alarm and tag configuration requires no changes when the underlying I/O mapping is preserved through the ET 200SP migration. The overall result is a modernized, compact, and diagnostics-rich distributed I/O architecture that extends the operational life of the control system by a decade or more.

Retrofit Guidance FAQ

Q: Can I reuse my existing PROFIBUS cable and connectors?
Yes. The 6ES7155-6BU00-0CN0 uses a standard 9-pin Sub-D PROFIBUS connector. Existing cables, connectors, and termination resistors are fully reusable provided the cable meets PROFIBUS Type A specification (impedance 135–165 Ω, capacitance <30 pF/m).

Q: Do I need to modify my PLC program after replacing the interface module?
In most cases, no. If the DP slave address and GSD-based I/O configuration are preserved, the PLC program’s I/O addressing remains valid. Only the hardware configuration file in TIA Portal or STEP 7 needs to be updated to reflect the new module type, followed by a download to the CPU.

Q: Is the PROFIBUS address setting retained after power cycling?
Yes. The PROFIBUS address is set via hardware selector switches on the 6ES7155-6BU00-0CN0 and is non-volatile. It does not require software configuration and is not lost during power cycles or firmware updates.

Q: What happens to my HMI alarm displays during the cutover?
If the I/O mapping and DP slave address are unchanged, HMI alarm tags linked to PLC data blocks or I/O addresses will continue to function without modification. A brief station restart during module swap will generate a temporary BF (Bus Fault) alarm that clears automatically once the new module is online.

Q: Can the ET 200SP station fit in the same cabinet space as the ET 200S station it replaces?
Yes, and typically with space to spare. The ET 200SP form factor is significantly more compact than ET 200S or ET 200M, often reducing DIN rail length requirements by 40–60%. This allows additional I/O capacity to be added within the existing enclosure without mechanical modifications.

Q: What communication baud rates are supported, and do I need to reconfigure the PROFIBUS segment?
The 6ES7155-6BU00-0CN0 auto-detects the baud rate set by the DP master, supporting all standard rates from 9.6 kbps to 12 Mbps. No baud rate reconfiguration is required on the segment.

Warranty Assurance

Every 6ES7155-6BU00-0CN0 unit shipped by TOPNLMS is covered by a 12-month warranty from the date of delivery. Prior to dispatch, each module undergoes functional verification including power-on self-test, communication interface check, and visual inspection for physical integrity. Units are shipped in anti-static packaging with original labeling and documentation where available.

In the event of a confirmed defect within the warranty period, TOPNLMS provides replacement dispatch within 3 business days of fault confirmation, with return shipping costs covered for verified warranty claims. Our technical support team is available to assist with installation queries, compatibility verification, and commissioning guidance via email at [email protected] or by phone at +86 18359293191.

Stock is maintained in Xiamen, China, with express international shipping options available to minimize lead time for urgent replacement requirements. Most orders to Southeast Asia, the Middle East, and Europe are fulfilled within 3–7 business days via DHL, FedEx, or UPS, with full tracking provided at time of dispatch.

TOPNLMS specializes in industrial automation components for mission-critical applications. Our procurement team sources directly from authorized distribution channels and verified secondary market suppliers, with each unit traceable to its origin. We understand that unplanned downtime in a PROFIBUS-based control system is measured in production losses per hour — our fulfillment process is designed to get the right module to your site as fast as possible.

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