Product Core Brief

• Model: F3LC21-1N
• Brand: YOKOGAWA
• Series: CENTUM CS 3000 / F3 Series I/O
• Core Function: Multi-link communication module for serial data exchange between the FCS and external serial devices.
• Product Type: DCS Serial Communication / Multi-Link Module
• Key Specs: F3 Series I/O slot | Serial multi-link interface | CENTUM CS 3000 FCS compatible
• Condition: New Surplus / Tested

Key Technical Specifications

• Module Type: Multi-Link Module (F3LC21 series)
• Suffix Code: -1N
• System Compatibility: CENTUM CS 3000 FCS (F3 Series I/O)
• Communication Type: Serial multi-link communication
• Installation: F3 Series I/O slot in Field Control Station
• Application: Connecting external serial devices to the FCS
• Series Family: F3LC series communication modules
• Typical Use: Protocol conversion, serial device integration, data exchange with non-DCS equipment
• Condition: Surplus / Tested

Product Introduction (No Fluff)

The F3LC21-1N is a multi-link communication module from the YOKOGAWA F3 Series I/O lineup, used in CENTUM CS 3000 Field Control Stations. It provides a serial communication interface that allows the FCS to exchange data with external serial devices, instrumentation, or third-party equipment that does not natively speak the DCS protocol.

For plants maintaining legacy CS 3000 installations, this module is a targeted replacement when integrating serial instruments, legacy analyzers, or peripheral devices into the control strategy. Because serial communication modules are often discontinued by OEMs, verified surplus stock is a practical way to keep these interfaces operational without redesigning the entire communication architecture.

QA & Testing SOP (Dynamic & Transparent)

Every communication module goes through the same bench verification we’d run before trusting it on a live FCS backplane:

1. Visual & authenticity check: Inspect housing, label, connector pins, and solder joints for rework, corrosion, or counterfeit indicators.
2. Connector & pin inspection: Verify the serial port connector and backplane pin alignment—oxidized or bent pins are a common failure mode on older F3 communication modules.
3. Bench power-up test: Apply rated power on an OEM-compatible F3 test rack and confirm module initialization without fault LEDs.
4. Serial communication verification: Confirm the module responds on the serial interface and maintains stable communication with a test device at the expected baud rate and protocol settings.
5. ESD-safe packaging: After testing, the unit is sealed in anti-static shielding with moisture barrier protection for shipment.

Installation Pitfalls & Guide (Engineer to Engineer)

❗ Do not confuse F3LC21-1N with F3LC11-1N or F3LC12-1N. The F3LC11 is a PC computer link module (serial half-duplex), while the F3LC21 is a multi-link module. Different protocol support, different application.

❗ Check baud rate and protocol settings before install. Serial communication modules must match the external device’s settings exactly. A mismatch looks like a hardware fault but is almost always a configuration issue.

❗ Verify backplane slot compatibility. F3 modules fit specific FCS slot types. Forcing a module into the wrong slot can damage backplane pins.

❗ Grounding matters for serial links. Poor grounding between the FCS and the external device can introduce noise on the serial line, causing intermittent communication drops.

Replacement steps:

1. Pre-install: Confirm slot position, communication settings, and backplane power state.
2. Removal: Power down the FCS slot if possible; release the module latch and withdraw straight out.
3. Install: Align pins carefully, seat fully, and secure the latch. Connect serial cabling with proper grounding.
4. Power-on test: Restore power, verify LED status, and confirm serial communication with the external device.

Technical FAQ

What he do? It is a multi-link serial communication module for the YOKOGAWA F3 Series I/O, used in CENTUM CS 3000 FCS to connect external serial devices to the control system.

Is this compatible with F3LC11-1N? They are in the same F3LC communication family but serve different roles. The F3LC11-1N is a PC computer link module, while the F3LC21-1N is a multi-link module. They are not directly interchangeable—always match the exact suffix to your system configuration.

Can I use this for RS-232 or RS-485 communication? The F3LC21-1N provides serial multi-link communication. The exact electrical interface (RS-232, RS-422, RS-485) depends on the specific variant and configuration. Confirm the physical layer requirements against your external device before ordering.

Is this module still available from Yokogawa? The F3 Series I/O is a legacy platform. New OEM stock may be limited or discontinued. Surplus and tested units are often the most practical option for maintenance and expansion of existing CS 3000 systems.

What is the warranty? Surplus and tested units typically carry a 12-month functional warranty. Confirm exact terms at checkout, as condition varies by lot.