Hollysys FM171B Digital Output Module

Technical Dossier

Product Details And Specifications

Hollysys FM100 Series Technical Notes

The Hollysys FM100 series constitutes the core I/O and controller module family deployed within the Hollysys MACS (Modular Advanced Control System) DCS platform. This series holds a significant installed base across heavy industrial sectors globally, including petrochemical refineries, coal chemical plants, nuclear power auxiliary systems, and large-scale thermal power generation facilities throughout Asia-Pacific and the Middle East. The FM100 series modules are designed for high-density, rack-mounted deployment within the MACS-S and MACS-K controller cabinets, operating under IEC 61131-3 programming standards and supporting redundant backplane communication architectures. Their long production lifecycle — spanning from the early 2000s through the current decade — has resulted in a substantial installed base requiring ongoing spare parts support, including for models that have entered end-of-life status.

The Evolution of FM100 Series Architecture

The FM100 series was introduced as part of Hollysys's first-generation MACS DCS platform, targeting large-scale process automation in Chinese state-owned industrial enterprises. Early modules in the series used parallel backplane communication with proprietary Hollysys bus protocols. As the platform matured into the MACS-S generation, the backplane architecture transitioned to a high-speed serial ring bus, improving noise immunity and enabling longer cabinet runs. The FM171 sub-family — which includes the FM171B — represents the digital output tier of this architecture, providing 24VDC or relay-contact discrete outputs for field device actuation. Compatibility between early FM100 modules and later MACS-S racks requires verification of backplane revision levels; cross-generation substitution is not universally supported without firmware alignment. The series has progressively entered a mature/end-of-life phase, with Hollysys transitioning new projects to the MACS-K and HOLLiAS-MACS 6.x platforms. This makes long-term spare parts availability from specialist distributors a critical operational requirement for existing installations.

FM100 Series Full Catalog & Functionalities (SKU List)

The following catalog covers verified SKUs within the Hollysys FM100 / MACS DCS module family, organized by functional category. Each model represents a discrete line-replaceable unit (LRU) within the MACS rack system.

Controller & CPU Modules

• FM131: Main controller module, MACS-S platform, dual-redundancy capable, 32-bit CPU
• FM131A: Enhanced main controller, increased SRAM, extended I/O scan rate support
• FM131B: Revised controller with updated firmware loader and USB configuration port
• FM148: Redundant controller communication module, ring bus master arbitration

Digital Input (DI) Modules

• FM151: 16-channel 24VDC digital input module, isolated, MACS-S backplane
• FM151A: 32-channel 24VDC DI, high-density variant, dual-row terminal block
• FM152: 16-channel 120VAC digital input module, field-side isolation
• FM153: 16-channel dry contact digital input, for valve position feedback circuits

Digital Output (DO) Modules

• FM171: 16-channel 24VDC digital output module, transistor sink type, 0.5A per channel
• FM171A: 16-channel DO with enhanced short-circuit protection and diagnostic LED per channel
• FM171B: 16-channel 24VDC digital output, revised output driver IC, improved thermal derating; direct replacement for FM171 and FM171A in MACS-S racks
• FM172: 8-channel relay output module, SPDT contacts, 2A/250VAC rated, for motor starter and solenoid valve control
• FM173: 16-channel relay output module, SPST-NO contacts, high-density relay DO for discrete actuator control

Analog Input (AI) Modules

• FM161: 8-channel analog input, 4–20mA / 0–10V selectable, 16-bit ADC resolution
• FM161A: 16-channel AI, multiplexed, 4–20mA, HART pass-through capable on select channels
• FM162: 8-channel thermocouple input module, J/K/T/E/R/S/B type, cold junction compensated
• FM163: 8-channel RTD input module, PT100/PT1000, 3-wire and 4-wire configuration

Analog Output (AO) Modules

• FM181: 4-channel analog output, 4–20mA, 12-bit DAC, for control valve positioner drives
• FM181A: 8-channel AO, 4–20mA, 14-bit DAC, improved linearity for precision flow control

Communication & Specialty Modules

• FM143: PROFIBUS-DP communication adapter, DP-V1 master, for field device integration
• FM144: Modbus RTU/TCP gateway module, serial and Ethernet dual-port
• FM191: Power supply module, 24VDC rack bus, 5A output, redundancy-capable with hot-swap