ABB PROFIBUS Redundancy Link Modules

Technical Dossier

Product Details And Specifications

ABB RLM01 / PROFIBUS Series: Comprehensive Module Range and Technical Overview

The ABB PROFIBUS Redundancy Link Module (RLM01) series is a purpose-engineered communication infrastructure component within ABB's AC800M Distributed Control System (DCS) platform. Deployed across global heavy-process industries — including petrochemical refineries, nuclear power generation facilities, offshore oil & gas platforms, and large-scale chemical plants — these modules serve as the physical and logical bridge between the AC800M controller backplane and PROFIBUS DP field device networks.

The RLM01 and its associated ecosystem of PROFIBUS interface modules are installed in facilities where continuous process availability is non-negotiable. Redundant PROFIBUS topologies enabled by this module family allow field device communication to persist through single-point hardware failures, a requirement mandated by IEC 61511 functional safety standards in many process sectors. The installed base of ABB AC800M systems globally — estimated in the tens of thousands of controller nodes — ensures sustained demand for RLM01-series spare parts well beyond the product's commercial production lifecycle.

The Evolution of RLM01 / PROFIBUS Architecture in ABB DCS Systems

ABB's integration of PROFIBUS DP into its process automation architecture began in earnest with the S800 I/O system and the AC800M controller platform, introduced in the late 1990s and progressively refined through the 2000s and 2010s. The PROFIBUS Redundancy Link Module (RLM01) was developed to address a specific architectural gap: standard PROFIBUS DP does not natively support media redundancy at the physical layer. ABB's RLM01 implements a proprietary redundancy protocol layered over PROFIBUS DP, enabling dual-cable ring or parallel redundant topologies.

Early Architecture (AC800M v4.x – v5.x): Initial deployments used single RLM01 modules per PROFIBUS segment with manual failover. Firmware compatibility was tightly coupled to the PM851/PM856 controller module generation. Integration with the S800 I/O system required specific CI854 or CI854A communication interface modules on the controller side.

Mature Architecture (AC800M v5.1 – v6.x): Redundant RLM01 pairs became standard practice. The introduction of the CI854B and CI858 modules expanded PROFIBUS DP bandwidth and improved diagnostic transparency via PROFIBUS PA integration. The RLM01 firmware was updated to support faster fault detection and switchover times, reducing process impact during link failures.

Modern Replacement Path (AC800M v6.x onward): ABB has progressively migrated new installations toward PROFINET-based I/O with the CI871 and CI873 communication interfaces. However, the installed base of PROFIBUS-based S800 I/O systems remains extensive. ABB's official position supports continued operation of PROFIBUS-based AC800M systems with spare parts availability commitments, though the RLM01 itself has entered a mature/end-of-active-production phase. Third-party spare parts suppliers such as DriveKNMS provide lifecycle extension support for this module family.

RLM01 & PROFIBUS Full Catalog & Functionalities (SKU List)

The following SKUs represent the core components of the ABB AC800M PROFIBUS communication and redundancy infrastructure. All models listed are verified members of the ABB S800 / AC800M ecosystem.

Redundancy Link Modules

• 3BDZ000398R1 (RLM01): PROFIBUS DP redundancy link module; enables dual-redundant PROFIBUS segment topology for S800 I/O stations.
• 3BDZ000398R2 (RLM01B): Revised hardware revision of RLM01 with improved EMC shielding and extended operating temperature range.

PROFIBUS Communication Interface Modules (Controller Side)

• 3BSE025255R1 (CI854): PROFIBUS DP master communication interface for AC800M; supports up to 125 slave devices per segment.
• 3BSE025255R2 (CI854A): Updated CI854 with enhanced diagnostic buffer and improved hot-swap capability.
• 3BSE025255R3 (CI854B): Third-generation PROFIBUS DP master; supports PROFIBUS PA segment coupler integration and extended baud rates.
• 3BSE018168R1 (CI858): Dual-port PROFIBUS DP/PA communication interface; supports simultaneous DP and PA segment management from a single module slot.

S800 I/O Station Modules (Field Side — PROFIBUS Connected)

• 3BSE020512R1 (AI810): 8-channel analog input module; 4–20 mA / 0–10 V; HART-transparent on selected channels.
• 3BSE020514R1 (AO810): 8-channel analog output module; 4–20 mA; supports HART pass-through communication.
• 3BSE020508R1 (DI810): 16-channel digital input module; 24 VDC; standard process signal acquisition.
• 3BSE020510R1 (DO810): 16-channel digital output module; 24 VDC / 0.5 A per channel; solid-state switching.
• 3BSE008516R1 (AI820): 8-channel analog input module; RTD/thermocouple inputs; supports Pt100, Pt1000, J, K, T type sensors.
• 3BSE008518R1 (AO820): 8-channel analog output module; voltage output variant; 0–10 V / ±10 V configurable.
• 3BSE008514R1 (DI820): 16-channel digital input module; 120 VAC input rated; for legacy AC field signal environments.
• 3BSE008520R1 (DO820): 8-channel digital output module; relay output type; 250 VAC / 5 A per channel.
• 3BSE013088R1 (TB820): PROFIBUS DP termination and bus connection module for S800 I/O station baseplate.
• 3BSE013089R1 (TB820V2): Updated TB820 with integrated bus termination resistors and improved connector locking mechanism.

Power Supply Modules (S800 Station)

• 3BSE023784R1 (SD821): 24 VDC / 3 A power supply module for S800 I/O station; DIN rail mount; redundancy-capable.
• 3BSE023785R1 (SD822): 24 VDC / 6 A power supply module; higher current capacity for dense I/O station configurations.
• 3BSE023786R1 (SD823): Redundant power supply module pair; automatic load sharing and failover for critical S800 stations.

Sourcing Hard-to-Find & Obsolete RLM01 Series Parts

The ABB RLM01 and associated PROFIBUS communication modules have entered a mature product lifecycle phase. ABB's standard spare parts program provides limited stock depth for older hardware revisions, and lead times through official channels can extend to 16–26 weeks for low-volume SKUs. For process facilities operating on extended maintenance cycles — common in nuclear, refinery, and chemical plant environments where DCS replacement projects span 10–15 years — this supply gap creates operational risk.

DriveKNMS maintains a dedicated inventory program for ABB AC800M PROFIBUS module families, including the RLM01, CI854/CI854A/CI854B, CI858, and associated S800 I/O modules. Our sourcing capabilities include:

• New-in-box (NIB) stock: Original ABB-manufactured units from authorized distribution channels, held in climate-controlled storage.
• Tested surplus: Decommissioned units from plant upgrades, fully tested to ABB factory functional specifications before resale.
• Cross-revision compatibility advisory: Guidance on hardware revision interchangeability (e.g., CI854 vs. CI854A vs. CI854B) to prevent firmware incompatibility issues during emergency replacements.
• Emergency dispatch: Priority fulfillment for unplanned outage scenarios, with same-day shipping available for in-stock items.

Quality Control for the RLM01 / PROFIBUS Range

PROFIBUS redundancy link modules and communication interface modules present specific test challenges due to their dual-port bus architecture, firmware-dependent behavior, and sensitivity to backplane connector integrity. DriveKNMS applies a structured test protocol to all RLM01-series units prior to dispatch:

• Backplane connector inspection: Physical inspection of all S800 baseplate connector pins under 10x magnification. Bent, corroded, or worn pins are documented and units are rejected or repaired to specification.
• PROFIBUS segment simulation: Each RLM01 unit is connected to a live PROFIBUS DP test segment with a minimum of four slave devices. Redundancy switchover is triggered and measured; switchover time must fall within ABB's specified range (<50 ms for standard configurations).
• Firmware version verification: Firmware revision is read and logged. Units with firmware below minimum supported versions for AC800M v5.1 compatibility are flagged and updated where possible, or sold with explicit version disclosure.
• Communication interface loopback test: CI854/CI858 modules undergo full PROFIBUS DP master loopback testing, verifying both physical layer signal integrity and protocol-layer message handling.
• Burn-in cycle: All refurbished units undergo a 48-hour powered burn-in cycle at ambient temperature to screen for early-life component failures before shipment.
• Packaging and ESD protection: All modules are shipped in anti-static bags with foam cushioning. Humidity indicator cards are included for long-distance shipments.