2. Model Definition

51304362: Base part number for multi-port isolated RS485 serial communication FTA, dedicated pairing with MC-COM68 serial IOP module

-250: Advanced heavy reinforced industrial PCB grade

Extra-thick heavy-duty full-board conformal coating, outstanding resistance to salt fog, sustained high humidity, heavy dust and mild acidic/alkaline fumes

Oversized high-energy bidirectional ESD and transient surge suppression components

Multi-stage cascaded differential EMI filter network for extremely electrically noisy heavy industrial environments

Jumper configurable RS485 bus termination & line bias resistor arrays

Nickel-plated compression terminals and PCB solder pads for long-term anti-oxidation

Matched IOP Hardware: MC-COM68 (Compact UCN bus multi-port galvanically isolated RS485 serial communication IOP card)

Incompatible Hardware: AI/AO analog FTA, discrete DI/transistor/relay DO FTA, pulse counter FTA, LLAI temperature FTA

3. Technical Specifications

Communication Ports: Multiple fully galvanically isolated RS485 differential serial ports

Supported Protocols: Modbus RTU, Honeywell proprietary serial protocol, standard asynchronous serial communication

Signal Interface: Balanced differential RS485 A/B lines with complete port-to-port galvanic isolation

PCB Protection: Extra-thick heavy-duty full conformal coating; flammability rating UL94 V0

Terminal Type: Nickel-plated compression screw terminals, fits solid/stranded copper wire up to 14 AWG

Form Factor: Standard Size B footprint, snap-on mounting for 35 mm standard DIN rail

Operating Ambient: 0℃ ~ +60℃ (indoor cabinet only); extended tolerance for high humidity, salt mist and mild corrosion compared to -100/-150/-200 grades

Circuit Architecture

Multi-stage per-port differential low-pass EMI filtering for data line noise elimination

Ultra-high-capacity bidirectional ESD and transient voltage surge suppression

Jumper-selectable bus termination and line bias resistor networks for flexible bus topology

Segregated isolated ground plane layout to eliminate inter-port ground loop circulating currents

Redundancy Compatibility: Fully supports primary/standby redundant MC-COM68 IOP architecture; hot-swap IOP card replacement allowed

Approximate Unit Weight: 0.365 kg

4. Interface & Communication Configuration

Inner IOP Connection: Locking flat ribbon cable connector directly mates to MC-COM68 pin headers. Built-in cable strain relief prevents pin header deformation or fracture caused by pulling tension from field communication wiring harnesses. No independent communication processor; serial bus data is transmitted to DCS controller over UCN control bus via paired MC-COM68 IOP module.

Field Outer Terminals: Clearly silkscreened nickel-plated A/B differential signal terminals, shield earth ground and dedicated jumper positions for bus termination per serial port. Physical isolation partitions separate individual ports to minimize cross-port data crosstalk.

Auxiliary Isolation Power: Cabinet 24VDC system power supplies isolation barrier auxiliary power through MC-COM68 IOP interface; FTA remains passive without local voltage regulation circuits.

5. Core Functions

Cable Strain Relief: Protects delicate MC-COM68 IOP pin headers from mechanical damage under long-term wiring tension.

Advanced Multi-Stage Differential Noise Rejection: Cascaded high-performance EMI filters suppress severe interference from large VFD banks, high-current contactors and medium-voltage switchgear, drastically reducing garbled data frames, Modbus timeouts and intermittent communication dropouts.

Heavy-Duty ESD & Surge Protection: Oversized clamping components absorb strong electrostatic discharge, wiring-induced voltage spikes and minor lightning induction surges, delivering maximum protection for sensitive RS485 transceiver circuits on MC-COM68 IOP card.

Premium Anti-Corrosion Environmental Barrier: Extra-thick conformal coating fully encapsulates PCB substrates, solder pads, copper traces and passive components. It ensures stable 24/7 uninterrupted serial operation in coastal, offshore auxiliary, tropical high-humidity and mildly corrosive chemical plant cabinets. Nickel plating on terminals and pads avoids oxidation and contact resistance drift over long service cycles.

Flexible Configurable Bus Topology: Onboard jumpers enable quick setup of RS485 termination and line biasing without external resistor blocks, adapting to short-distance and long-distance daisy-chain bus layouts.

Isolated Port Ground Design: Separated grounding planes eliminate destructive ground loop currents between DCS system and remote field serial devices, the primary root cause of unstable Modbus communication.

Redundancy Hot-Swap Capability: Standby MC-COM68 IOP cards can be replaced online without disconnecting critical communication links to smart instruments, motor drives and process analyzers.

6. Application Scenarios

Applicable Industries (Honeywell Experion PKS UCN DCS Platform)

Coastal petrochemical complexes, offshore auxiliary control cabinets, chemical processing plants, thermal power stations, oil & gas refineries, pulp & paper mills, metallurgical furnaces, high-humidity water treatment plants, tropical pharmaceutical batch production lines.

Serial Communication Connection Loops

Modbus smart transmitters, online process analyzers, variable frequency motor drives (VFDs), motor protection relays, remote slave PLCs, batch weighing systems, gas chromatographs, continuous emission monitoring systems (CEMS).

Cabinet Deployment: Dedicated compact terminal base for multi-port serial communication slots inside high-density space-saving DCS I/O control cabinets.

7. Operation, Wiring & Maintenance Instructions

Wiring Standards

Maintain consistent A/B differential polarity across the entire RS485 bus segment; daisy-chain topology is strongly recommended over star topology for long cable runs.

Use shielded twisted-pair communication cable; implement single-point shield grounding only at cabinet FTA side to prevent ground loop current formation.

Enable onboard termination jumper only at the two extreme physical endpoints of each RS485 bus; all intermediate nodes must remain unterminated.

Spare Part Interchangeability

51304362-250 shares identical serial signal conditioning circuit topology with -100/-150/-200 variants for direct emergency field substitution. The -250 heavy-duty grade is specified for coastal, salt-laden, highly humid or lightly corrosive cabinet environments where standard -200 grade lacks sufficient long-term reliability margin.

Standard Fault Troubleshooting Flow

Modbus timeout / no device response / corrupted data frames → Retighten compression terminal screws → Verify uniform A/B bus polarity → Inspect termination jumper configuration → Check shield grounding integrity → Confirm ribbon cable fully seated and locked into IOP header → Diagnose operational health of paired MC-COM68 IOP card.