Component Snapshot At-a-Glance
- Model: FCM100ET
- Alt. P/N: P0926GS
- Product Series: Foxboro I/A Series DCS (Evo Compact 200 Series)
- Hardware Type: Redundant fieldbus communication bridge module
- Key Feature: 100Mbps Ethernet (fiber) ↔ 2Mbps fieldbus electrical conversion
- Primary Field Use: Connects DCS controllers to 200 Series FBM I/O modules across plant racks.
Hard-Numbers: Technical Specifications
- Protocol Support: I/A Series proprietary fieldbus, Ethernet 100BaseFX
- Port Count: 1×fiber Ethernet, 1×2Mbps fieldbus
- Data Rate: 100Mbps (fiber) / 2Mbps (fieldbus)
- Operating Temperature: 0°C to +60°C (G3 environment)
- Isolation Rating: 1500V RMS fiber-to-fieldbus isolation
- Power Draw: 24VDC, 10W max; redundant power compatible
- Max Nodes: 32×200 Series FBMs; up to 128 with FEM100 expansion
- Processor: 32-bit RISC, 0.1μs/Boolean instruction
- Memory: 8MB program, 4MB data
- Hot Swap: Yes, live rack replacement
- Dimensions: 140×165×45mm; weight 0.6kg
The Real-World Problem It Solves
Long copper fieldbus runs pick up EMI and ground loops, causing CRC errors and intermittent I/O drops. Non-redundant comm modules become single points of failure that take down entire racks.
Where you’ll typically find it:
- Power plant boiler/turbine I/O racks linking FBMs to Evo controllers
- Refinery process units with distributed 200 Series I/O clusters
- Chemical plants needing fiber-backed, noise-immune fieldbus links
This module eliminates copper-run noise and provides redundant comm paths to keep I/O online.
Hardware Architecture & Under-the-Hood Logic
is a dedicated bridge with its own RISC processor and isolated transceiver. It terminates fiber Ethernet and drives the 2Mbps fieldbus backplane.
- 100BaseFX fiber receives controller data; optical isolation blocks ground loops.
- Onboard RISC processor strips Ethernet headers, formats fieldbus frames.
- Differential line drivers output 2Mbps signals to the I/O rack backplane.
- Scans up to 32 FBMs, collecting analog/digital data into local buffers.
- Encodes fieldbus data, transmits back to controller via fiber Ethernet.
- Logs comm errors, link status, and FBM faults; reports to HMI.
Field Service Pitfalls: What Rookies Get Wrong
Mismatched Fiber Duplex/Speed
Techs often plug into 1Gbps switch ports or mismatched duplex, causing no-link or flapping ports.
- Field Rule: Force switch port to 100Mbps full duplex; use 62.5/125μm multimode fiber only.
Ignoring Redundancy Timing
Many pair redundant FCM100ETs but skip sync tuning, leading to switchover glitches and I/O blips.
- Quick Fix: Set redundant pair sync to 50ms; test switchover during low-load periods.
Overloading the Fieldbus Segment
New techs load 32 FBMs plus high-bandwidth modules, pushing latency over 100ms.
- Field Rule: Keep analog-heavy FBMs under 16 per segment; split high-speed I/O across two FCMs.
Commercial Availability & Pricing Note
Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.
