ABB Freelance DCS DP840 Module Termination Units

Technical Dossier

Product Details And Specifications

ABB Freelance DCS Series Technical Notes

The ABB Freelance DCS (also referenced under the AC 800F platform) is a distributed control system deployed extensively across global heavy industry — including petrochemical refineries, nuclear auxiliary systems, offshore platforms, pulp and paper mills, and pharmaceutical batch processing facilities. The Freelance platform is characterized by its modular I/O architecture, redundant CPU configurations, and FOUNDATION Fieldbus / PROFIBUS DP integration, making it one of ABB's most widely installed mid-range DCS solutions. The DP840 is a Module Termination Unit (MTU) within this ecosystem, providing the physical field wiring interface for I/O modules mounted on the DIN-rail carrier system.

The Evolution of Freelance DCS Architecture

ABB's Freelance DCS originated from the Elsag Bailey INFI 90 lineage and was formally rebranded and re-architected under the AC 800F designation in the early 2000s. The platform evolved through three distinct generations: the original Freelance 2000 (FLC2000) with proprietary fieldbus backplanes; the AC 800F R4.x generation introducing IEC 61131-3 programming and Ethernet-based engineering tools; and the current AC 800F R6.x / Freelance 2013 onward, which added redundant controller support, expanded HART pass-through, and integration with ABB Ability™ cloud diagnostics. The DP840 MTU family was introduced alongside the modular I/O expansion to decouple field wiring from module replacement — a critical design decision for plants requiring hot-swap capability without field cable disturbance. Compatibility between generations requires careful attention to backplane revision levels and firmware alignment, particularly when mixing DP840 units with older AI810, AO810, and DI810 I/O modules.

Freelance DCS Full Catalog & Functionalities (SKU List)

Controllers & CPUs

• PM864A: AC 800M redundant process controller, 32 MB application memory, dual Ethernet
• PM865A: AC 800M high-performance controller, extended I/O capacity, redundancy-ready
• PM891: Freelance AC 800F compact controller, integrated Ethernet, IEC 61131-3
• PM893: AC 800F redundant CPU module, hot-standby switchover <100ms

Analog Input (AI) Modules

• AI810: 8-channel analog input, 4–20 mA / 0–10 V, HART-capable per channel
• AI820: 8-channel analog input, high-speed sampling, thermocouple/RTD configurable
• AI830A: 8-channel analog input with HART, SIL 2 rated, redundancy support
• AI835A: 8-channel AI, intrinsically safe, ATEX Zone 1 certified

Analog Output (AO) Modules

• AO810V2: 8-channel analog output, 4–20 mA, HART pass-through, loop-powered
• AO820: 8-channel AO, high-resolution 16-bit DAC, short-circuit protected

Digital Input (DI) Modules

• DI810: 24-channel digital input, 24 VDC, optically isolated, group diagnostics
• DI820: 24-channel DI, 120 VAC input compatible, surge-protected
• DI830: 24-channel DI, SIL 2 rated, dual-channel safety input pairs

Digital Output (DO) Modules

• DO810: 24-channel digital output, 24 VDC, 0.5 A per channel, short-circuit detection
• DO820: 16-channel DO, relay output, 250 VAC / 2 A per contact

Module Termination Units (MTU) — DP840 Series

• DP840: Standard MTU for AI/AO/DI/DO modules, 40-terminal field wiring block, DIN-rail mount, screw-clamp terminals, compatible with AI810 / AO810 / DI810 / DO810 families
• DP841: MTU with integrated fusing, 40-terminal, individual channel fuse protection
• DP842: MTU for high-density I/O, extended terminal count, dual-module support
• DP845: MTU with HART multiplexer interface, supports HART 5/6/7 pass-through

Communication & Fieldbus Adapters

• CI840A: PROFIBUS DP adapter, 12 Mbit/s, redundant media support, DPV1 services
• CI854A: FOUNDATION Fieldbus H1 adapter, 31.25 kbit/s, 16 device addresses
• CI858: DeviceNet adapter, 500 kbit/s, 64 node capacity